Hetzner still haven't said anything to me about Spectre/Meltdown, or rebooted my VPS, so I'm not sure I trust them any more!
I can't think of an approach that would be more direct to their customers than seeing it on top of their customer homepage.
"The host systems will be updated to fix the vulnerabilities as soon as possible. The necessary reboots will be announced on Hetzner Status. You may subscribe to be notified. "
Anyway, the proof is in the 264 day uptime!