The way I’ve found this issue to work is through Resource Packs that I’ve created, and I should say that, when downloading other packs that seem to have set "min_engine_version" to, for example, 1.26.1, this issue does not occur, so I’m unbeknownst to whether or not this is just an issue on my end.
Steps to reproduce:
Create a small resource pack with the specified "min_engine_version"
Import your resource pack into Minecraft and activate it.
Observed result:
Once the texture pack begins loading in, Vibrant Visuals will automatically be disabled and locked.; these will unlock once the resource pack is deactivated.