Warning logs are usually polluted with stuff nobody wants to fix but try to wash their hands off with a log. Like deprecated calls or error logs that got demoted because it didn't matter in practice.

Anything that has a measurable impact on production should be logged above that, except if your system ignores log levels in the first place, but that's another can of worms.

Logging warnings are cowardly, you just push the decision to the log consumer to decide if the error should be acted on.

Warnings are just errors that no one wants to deal with.