alt Hacker NewsThis might be an indicator that PM isn't doing their job; PM should be able to answer you questions regarding what the business wants (= people who you're trying to serve). Developers, by the nature of interacting with domain, do become experts in the domain, but really it should be up to PM what the domain should be doing business-wise.
If that is what a PM needs then there aren't enough good PM to warrant a PM role for most products, so just make software engineers do that in most cases.
Edit: The main role of PM is to decide which features to build, not how those features should be built or how they should work. Someone has to decide what to build, that is the PM, but most PM are not very good at figuring out the best way for those features to work so its better if the programmers can talk to users directly there. Of course a PM could do that work if they are skilled at it, but most PM wont be.