Hi Holger!
This is not really fixed in linux-image-4.17.0-1-amd64.
I'm still having a little delay with 4.17.8-1
It should not. The kernel now takes more time to get the necessary entropy (actually before it was giving random values when it shouldn't).
A workaround is to install haveged, but beware that some people don't trust it enough.
For what I've saw having an encrypted disk helps.
Regards, Lisandro