You think a product manager was in any way involved with a function signature. I'm fairly certain this didn't come up in more detail than a requirement: "We need to add a way to call a macro...". And the story as told by the PM would be "...and so the engineers added a way".

I've worked with a bunch of PMs on technical products, APIs, etc. and I've rarely met anyone discussing that level of detail or willing or able to make such a decision.

The engineers chose a way that worked and it's likely the best way supported at the time, given the other comments I've read here on HN.