Yep, this is getting blown way out of proportion by all of these tiny scripts that just sit around connecting to themselves. Even pgbench is theoretical and intended for tuning; you're not going to hit your max tps in your Real Code that is doing Real Work.

In the real world, where code is doing real things besides just entering/exiting itself all day, I think it's going to be a stretch to see even a 5% performance impact, let alone 10%.