I'm going to do my best to flesh this out with you, but I haven't been on Tumblr in a bit and my discourseTM is probably rusty!
This ask is hella tricky IMO. On the one hand, I personally believe that queer experiences should run the gamut in media, because queer people are people, which means queer people can also die, obviously. But on the other hand, the trope is a trope because of the disproportionality therein. Since queer people are usually underrepresented at any given time, seeing them suffer or die often feels unnecessary. Queer people should be able to have stories that don't center around turmoil or being in the closet and romances that don't end with death or one of the partners realizing they were never queer at all and running forlorn into the arms of a member of the opposite sex.
In my experience, intention also matters. I, for my part, don't mind torturing or killing my characters when I write. I treat everyone the same. That is to say, anybody can get it! I'm here the ANGST. But it's worth understanding the motivation behind your literary choices. Why THIS character? Is it BECAUSE they are gay? Does their sexuality add to the turmoil surrounding them or is it just one factor of who they are? Those things make a difference to me.
If you're telling a story about a queer person's queer journey, and that is your intention, I would say to be honest about their story. Don't go for shock value or make them a pawn in someone else's pain. Tell THEIR story and convey the message without intentionally traumatizing your audience. If you're telling a story that has queer characters in it but doesn't center around said queerness, I'd say to be careful about how your queer characters are treated in comparison to your straight characters. Don't have one die right after they finally get to be with their same-sex partner (*cough cough* The 100 *cough*), and don't have them die just because it's shocking (*stares in Supernatural*), and definitely don't kill them in a traumatic way that highlights the stereotypes and disparity that their race or gender expression has seemingly brought upon them (RIP Poussey).
When all is said and done, gays can be buried. And they can be buried well. (Look at POSE as a great example of this) Just don't bury them for the sake of the heterosexual gaze. Queer people have had enough trauma in their lives, and while we deserve to have our stories told in all their multifaceted glory, it's also okay to give us some peace, love, tranquility, softness, and beauty along the way. That alone can also be our story.
To answer your ask more directly, when it comes to fics that have any canonically alive gay characters dead, it CAN count as burying your gays. I think it depends on how and why it's done. If it feels unnecessary, it probably is. If it feels intentionally traumatic, it probably is. TBH, we don't need those stories. We don't even really want them. So ask yourself why you'd want to tell that story in that way and what value it adds to the collective queer narrative before you hit publish.
I hope this is an adequate answer, but if not, thanks for getting my brain juices flowing anyway ;)