I think it would happen with any persona that Anthropic chose. I enjoyed the bouncy, optimistic style at first. I've since grown to hate it.

A terse and compliant robotic servant should've been the persona they chose, because that's probably 99% of what those wanting to use it for work expect.

how do they infuse this personality? do they train the human feedback providers with a certain personality?

If we assume the personalities come from human feedback, it would have to be some unholy amalgamation of those feedback providers right?