I don't know about that -- I've always understood that to be the role of the product manager, to have all the domain knowledge.

It's the PM's job to work with engineering to ensure that the requirements are correct, and that the built product meets those requirements. And in an agile setting, those conversations and verifications are happening every single sprint, so something can't go for too long without being caught.

If you don't have a PM, then sure I guess your engineering team had better have deep domain knowledge. But otherwise, no -- it's not engineering's responsibility. It's products's responsibility.