Which goes back to the point, maybe Product aren't master of the universe directing all the teams, but just another group of folks with relevant skills that should advise and advocate, but not direct the others groups, whom are the actual experts of their respective areas.
Listen, I've been around the block and I understand it's quite common for the PM or other similar softer roles to be given leadership.
I've seen this to the point where they both recruit and promote the techs themselves.
What I'm saying is it doesn't have to be like this. If the PMs job is to find and articulate value, and the Engineers job is to produce said value, on a well performing team, it's a match made in heaven.
A poor PM with dominance over tech will happily torpedo the Engineers career with little emphathy whilst doing so, so why do we assume tech leadership should be in a different department?
My opinion is align the Engineer KPIs with value, which aligns them with strong PMs, but allow them the autonomy to say no when it makes sense to.
Just an opinion tho :)