"Is there a reason the product owner can't speak both english and logic?"
Theoretically no, but it's a big ask for one person. In reply to this entire chain, I'd suggest that it's actually something for the technical lead and the Product Manager to work out in conjunction with each other. For any team past about 4 people, it's just going to be too much to expect someone to both be the technical lead and be in contact with the users enough to be able to make those decisions. (A bit of crosstraining may be good, but trying to avoid that specialization is probably asking for trouble.)
If the PM and the lead don't respect each other enough to make that work, you've got a people problem. There's a lot of people-problem ways to muck this up, unfortunately. (Most obviously, I'd contend that making the PM be above the tech lead is a very common failure case. If you can't trust anyone on the engineering team to have a roughly equal voice in the product design process... uhhh... that's a pretty big problem on its own!)