Yes, it is... ish.

The frame skipping code occurs when we serialise exceptions, and we pass a limit in. The limit is calculated on the main exception only. If the cause has a longer exception than the limit we calculated, you'd see this behaviour.

Probably need to make it possible to do per-exception processing of limit: I think via a callback or similar mechanism in traceback (because the cause might have thrown from some code that is also marked __unittest, so if we're honouring that, we should honour it within each exception.