I don't really see a basis for this argument. A character that's written to be inaccessible by the player as a love interest might not necessarily have more to say just because the lack of romance-specific dialogue frees up the word budget. Plot relevant dialogue and insight into their own character may be exactly the same with or without the bonus material.
From what I've read from the developers, that sounds about right. The idea that romances somehow impede friendship dialogue is off-base. The writers are very careful to make sure that the dialogue for the romance arcs doesn't trump the dialogue and story for the rest of the companions. They've had a few missteps (like Jack, imho,) but overall they've done a good job of making sure that the romances doesn't hog other content. I also have seen, judging from DG's old blog, that they prioritize the rest of the character first. They write them out and create their personalities, background, story and reasons for being a part of the the team. This includes their sexualities. Then, they look at the character and see if it would make a good romance without taking away from the story and dialogue for the rest of the character.
I mentioned this in another thread, but DG has stressed in the past that BioWare is under zero obligation to write these romances. They aren't forced to do this; there isn't anything in their contracts stating that they must have romances. DG was asked, I think last year at GaymerX, if BioWare was going to always do romances in all of their games. He said that when it comes to opening the "Pandora's Box of Romance Content*," it's not an automatic given that the game will include romance options. It really depended upon the content of the story and how it would flow in the game.
It's also quite telling to me that not all BioWare writers have characters for romance. For example, one of my favorite BioWare writers is Mary Kirby. She wrote, among others, Varric and Vivienne. If you note her character history, she doesn't write player LI arcs. No one has forced her to do so, as it should be. She writes what she wants.
So, not only is the idea that BioWare forces romance is off base, the idea that they completely define any of their characters based on their romance arc is ludicrous.
I have to wonder who would complain the loudest if the BioWare devs removed romances altogether, or if they decided not to include it in the next IP DG is working on. I know I wouldn't care all that much, so long as the friendships and characterization of the companions were solid.
*One of my favorite comments from DG regarding the volatile nature when it comes to fans reactions to the romance arcs.*