Don't take my word for it, though. It's something I've read here on the forums and I don't have any source to back it up. I still like this idea better than "We simply thought that Jacob is that kind of guy," or "We wanted to hurt Shepard because feels." Well, I mean, since it's already in the game, Jacob obviously is that kind of guy, but I guess I like to think that, from the outside perspective, it wasn't meant to be offensive, just pragmatic.
It's also true this sort of stuff happens in real life. But it's interesting how this sort of crap only happens to femShep. ManShep's sweethearts are never permanently taken away and every single one of them can be saved. In the end, femShep can eventually only have a happy relationship with... Kaidan or Garrus...? (If gay or kinda gay, then with Liara or Samantha. There's Kelly and Samara somewhere in there but they get so little content I tend to forget those are even options.) I don't care about the love interest's gender myself and I tend to play my characters accordingly, but I'm still glad I tend to pick those that turn into big puppies that love you forever. I like my fluff.
Yeah, it is a better reason than the ones you said, that's true. I actually also don't oppose guys leaving you, as you say, this can happen in real life too. I just find it bad because MShep has way more options and like you say, none of that crap happens with them. Couple that with FemShep's really weird flirty/pushy writing and... eh. We already talked so often about it 
I also don't care for gender and I'm happy to try out the girls as well, but when your only straight option is Kaidan, or Garrus which is only importable from ME2, then that's a first sign they definitely should have included either Jacob, no matter how many people didn't find him interesting enough, or James. 1 straight interest already leaves you with Thane. That should've been enough imo because it was also a logical ending due to his illness.
But oh well, can't have everything 
Damn I never thought of it that way, FemShep has a much worse time of it. You can get jiggy with Vega, would he stick with you at the end? Maybe not as he's DLC only.
Vega's romance content in Citadel DLC is cringeworthy
No, really, it's just unfortunate FemShep writing, she's too pushy and makes some bad comments. James's writing is awesome there imo and with a little more dignity from Shepard's side this could've been really amazing, because the idea behind their one-night stand is a really great one imo, but not the way they portrayed FemShep here. I was in luck because my FemShep that went after Vega was a broken and emotionally unstable character so it fit quite well to pursue him like that, but I feel bad for people who wanted a normal James romance.
James doesn't stick with you though, it's treated as your casual one-night stand: they f*cked, f*cked up and don't talk about it anymore.