The point of a product manager is to make a lot of decisions that don't have a clear answer. "Should we use websockets or REST for our chat client?" - easy technical call. "Which market segment should we target with our features?" - not so technical.
There are plenty of technical decisions that don't have a clear answer (e.g. which of 1000 web frameworks should we use?), and plenty of product decisions that do. The separation between roles has nothing to do with clarity but with the (sometimes fuzzy) difference between technical decisions and product decisions.
You're right that decisions regarding frameworks are often made for largely arational reasons, but I'm baffled by the claim that these are not technical decisions (unless you're just joking?). If they're not, does that mean that in your model it's the PM who decides which web framework and database the team uses?
In any case, even if my example were a bad example for some reason, there are definitely lots of technical decisions that are fuzzy. How could there not be?
