In Advanced mechanics > Composter you can find what kinds of things can be composted, but certain things listed can't be obtained ingame, bell peppers, for example. It's a minor thing and I don't know if these are planned to be implemented but it's a small enhancement thing if it requires a fix.

So these are vaguely, "planned to be implemented", they just are not obtainable. Given that this just lists the contents of a tag, I don't think unimplementing these further is of any good sense. @eerussianguy thoughts, otherwise I'd say this is "working as intended, pending possible future implementation of these plants".

It would be weird for us to
a) ask patchouli to check if items have a creative mode tab before displaying them / override that behavior ourselves somehow
b) have a separate tag for display in patchy
c) break/make needlessly harder any addon/datapack that may want to implement bell peppers by removing their attached data