It's a valid point, but it's not the whole story. When there is too much of a gap between the local scene and the global scene, there is an isolation effect.
But it doesn't mean these engineers live in their remote bubble. There will be a halo effect of showing the way to local talent, we've seen when subcontracting html integration to a remote shop. Once the contract and legal framing was established, it was easier for us to ask their junior member to do administration tasks or other basic data entry tasks.
The other path is for these higher level engineers to move directly to high level positions in local firm. You'll see a junior engineer by EU standards move to a CTO like position in a local company or startup.
All in all, I think the local part still tremendously benefits from having highly competent remote workers.