Product teams are very busy people focused on release delivery schedules. They work very long, stressful hours on that focus, and participating here would cause them to not meet assigned project deliverables, or impact the schedule of other members of that team. From personal experience on non-Apple product teams, I can say without exception that one is completely focused on their deliverables.
It would not surprise me if Apple had very strict internal security policies about employees commenting on these public communities. The only Apple-badged staff that are permitted to reply to posts in these public communities are the Community Specialists assigned to the Apple hosting team, and these individuals are not members of product teams.