It’s curious when significant contributors leave Apple to explore emerging ideas elsewhere. One would think that Apple is encouraging its product managers to copy useful features or improve on them.
A helpful decoder ring when reading about Apple:
1) "Product managers" are marketing employees who sit in on some high level design meetings and liaise with the marketing management chain. No engineers report to them. They do not own the features. They do not run the show. It is a fluff title.
2) "Engineering managers" are engineering managers who are on the hook for everything related to the feature. The engineers report to them. And they frequently do at least bits of engineering themselves.
Any time you see anything attributed to a product manager, feel free to roll your eyes and move on.