Tuckey does some funky stuff with logging. It basically has its own thing, that can delegate to slf4j, but if that is not enabled then it will basically end up logging using the ServletContext log() methods (or stderr/stdout).
These methods kind of suck, as they have no way to specify a severity or category. In our impl the version without an exception logs at INFO, the version with logs at ERROR. Thinking about it these should really have their own category to make it clear what is going on here.
Other than adding a slf4j bridge and making it use slf4j somehow I don't know if there is much you can do.
Stuart