Unexpected concurrency-related compiler warning

I have something like the following. On the let b1... line in the Task I get a compiler warning in Xcode: Capture on non-Sendable type 'PT.Type' in an isolated closure. On the let b2... line there is no warning. I read the linked documentation on the error and tried to put a constraint on the protocol protocol P: AnyObject where P.Type: SendableMetatype but that doesn't help. Am I doing something wrong here or is that a compiler error? What could possibly be the difference between the static ...