The weirdest boolean for me is the "is secure" flag of the web platform, that is true if the site is loaded via https with a valid cert or is served from localhost - and that decides if any advanced browser features are available or not.

It makes sense given the history of the web, but its semantics are pretty much the same as (old) Twitter's blue checkmark.

Both essentially say "the entity you're interacting with is really the one you believe they are" - but neither makes any attempt to actually find out what my belief is, nor do they give me any information to verify that belief myself. It's just a "trust me" in form of a boolean.