I indeed missed the business part but I won’t recommend business goals over shadow user experience which it does when PMs with strong and only business backgrounds want to shove all content above the fold.
UX is the primary thing which sells or converts.
Fresh ideas can be gathered by not just PMs but any new employee joining a the company. The difference is, since PM is considered an elite role in a young startup their ideas are taken seriously whether they have context or not.
I don’t have a notion against PMs, I had really good relations with the PMs of my previous company but hiring external PMs is really shitty in agile environments especially in a country like India where people become PMs in like 1–2 years. I would rather have a person with context try to learn business objectives than a person with business context try to learn context.