I'm not an app developper. I make third-party colorschemes for Vim, which I assume are downloaded, installed, and used by people on their own volition, after they have looked at, and liked, the screenshots. Moreover, I take great care to make sure they are still usable in 16c, within reason.

Because all my work is based on 16-255, I can actually guarantee to my users that, given a properly configured terminal emulator, they will get the colors on the screenshots.

If I can't rely on 16-255 to be fixed anymore, then I won't be able to make any promise anymore. In practice, it just means adding a caveat in the README.md, but I'd prefer not to. Here's hoping this breaking change gets hidden behind a checkbox/flag.