They are not even the first people to try this stunt. That is trying to save a failing , and increasingly unpopular show with a last minute lesbian pairing goes back to Korrasami. And as shield from criticism from bad writing.
Are they even a good couple? I mean the show and all the characters tell us they are so great together. And they love to tell us how Blake and Yang are very close with each other. But we have hardly ever seen that.
I give them props for setting this up a few volumes back, but there’s no way this was planned from the start. Blake had a boyfriend before the series even began. And Yang was literally shown spying on the men showers because she was horny for men. Yes it was the chibi spin off. But it was still made and approved by RT.
Now they are trying to gaslight us to tell us they were always hardcore lesbians? Yeah not buying It. This was an obvious retcon to appeal to terminally online shippers.
Still I am even open to the idea that it could work. But the writers are seriously making a poor job selling it.