Yes, they state as much when you order anything and talked about it at length when they introduced the US offering.

They're shipping their specialized server systems to select providers for housing, essentially. Most maintenance is done remotely... aside from replacing faulty hardware etc

Hetzner's US cloud zones are colocated in someone else's facility (AFAICT they don't specify where): https://docs.hetzner.com/cloud/general/locations/#are-the-se...