If it's coming out of nowhere because it was a late addition to bring in a new reader base, yep, it's meh. (Not more or less than any late, awkward addition for the same reasons, though).
BUT. It is actually a real issue for creators even when they legitimately, from the beginning, have the idea of a non-romance story with some LGBT themes or a romance subplots. One issue that pretty much does not exist with straight couples, even if it's exactly the same, objectively.
I had very little comic background when I started mine and never had even read a webcomic. But one if the first issue I encountered was just that. Do I have to 'warn' (how horrible!) and, for other reasons/public, 'advertise', that there will be strong LGBT themes, in later chapters, in a story that has little to do with romance?
Well, people already writting comics gave me a bit of background and answers, and I understood quickly it was not a small issue, and not one with a easy answer either.
My story could completely look like 'I changed it and added LGBT themes because there is this new LGBT category on Tapas', even if it was planned like that for years.
So yes, there may be people who add these more or less awkwardly because they feel there is a readership for it right now. But there may be other who simply did not feel like warning people there would be such romance, and did not feel the need to advertise it either, because it's not the main subject.
A good test I think, would be to imagine a specific LGBT romance in these comics you read, as a straight romamce. If the romance is awkward because it was shoehorned last minute, it would feel as awkward whatever the genders, in my opinion (but I'm pan, so.. it's difficult to really imagine).