You can't romance Garrus without doing his loyalty quest. It is one of his romance requirement other than recruiting him in ME1.
So? That is the requirement for all of the romances in Mass Effect 2 as far as I can remember.
And compared to other LI characters, Garrus isn't romantically interested in either Shepard and always see them as friends first and would only consider the idea of "interspecies relationship" if you flirt him more than once.
So? Sometimes people develop feelings for each other or realize they have feelings for each other over the course of a relationship, sometimes a friendly relationship and sometimes a casual relationship.
Speaking of which, the relationship in Mass Effect 2 is initially a casual relationship that develops into a romantic relationship and continues as romantic in Mass Effect 3.
Additionally, there is little to no precedence for a turian and human relationship so that he hadn't considered a interspecies liason between a human and a turian is not exactly surprising.
The world is about to end and you still have to consistently convince him that you're interested in him because apparently he have insecurities. He is not a virginal teenage boy who need to come out of his shell because he haven't found his right girl yet.
I'd like to see some quote citation and video evidence to support this claim, please. This is partially because, as I've mentioned previously, Garrus says in Mass Effect 3 that he did not want to assume anything. This only make sense seeing as the relationship he and Shepard had in Mass Effect 2 was originally a casual liason that developed into an unspoken, romantic relationship between the two.
Also, when did I claim that Garrus was and I quote for emphasis; "-virginal teenage boy who need to come out of his shell because he haven't found his right girl yet."?
Even the line "Some women find facial scars attractive." isn't specifically directed to FemShep but women in general...
So? I have no context for the version of the line you are referring to so for all I know, the context is a romanced Garrus saying this line while teasingly implying that Shepard is one of the women that finds facial scars attractive. This only make senses given that it is more or less a joke between the two as evident in this scene where Shepard laughs when he says this;
Garrus: "The scars are starting to fade. I remember they drove you wild."
Shepard: "*laughs*"
The world is about to end and you still have to consistently convince him that you're interested in him because apparently he have insecurities. He is not a virginal teenage boy who need to come out of his shell because he haven't found his right girl yet. Even the line "Some women find facial scars attractive." isn't specifically directed to FemShep but women in general... which includes Tali, who he always imagine her having the face of an angel underneath her mask, who have success at getting him after two conversation via coms and she didn't do any special favors for him.
I know it happens but I cannot remember much, if any, of that. There is a precedence for turian and quarian relationships so that is not odd. It also seems likely that Tali was straightforward about wanting a romantic relationship or that they developed feelings for each other over the course of Mass Effect 3.
You could provide a quote of him saying he always imagined her as having the face of an angel since that sounds an odd line given that turian religion do not have angels but spirits but hey, that may simply be either the writers forgetting or me misremembering.
I am assume by "special favor", you are referring to loyalty mission in Mass Effect 2? As far as I know, Garrus is dead if his loyalty mission is not completed and if he is alive, his loyalty mission has been resolved one way or another meaning the thing that is preventing him from moving on has been dealt with.
And he was comfortable enough to show off that he have the Commander Shepard as his girlfriend and shower her with all his attention and yet he didn't know how to say "I love you, Shepard." because the vids didn't prepare him for it. Instead of Shepard having to order him to kiss her like an idiot, I would want to know exactly where he was going with the relationship because it seems like I have to stab his liver with a dagger and twisting it because he have to be critically injured for him to actually say what he felt. Not even Aric Jorgan do this to me and they romance the same Jennifer Hale.
I'm going to quote myself on this own because it seems to have been missed in the previous post; "Some couples don't feel the need to tell the other that they love them unless in special situations: this does not mean that they love each other less than a couple that does often tell the other that they love them. Shepard and Garrus seem to be more the former kind of couple."
Not even Aric Jorgan do this to me and they romance the same Jennifer Hale.
Thankfully, romances can and tend to differ from each other which I think is a great thing because it can help add variety and allow you to find a romance that is to your taste and preference. Speaking of which, your taste and preference seem to be more towards a relationship like the one in the Kaidan romance and generally romances where the couple in question frequently tell each other that they love each other. Personally, I like relationships where this is the case such as with Solas and relationships where this is not the case such as with Solas.