OK yeah this is a regression. It may depend on some CPU and kernel
interaction to set up the entropy pool, so the problem could appear on
some systems and not on others. I'm not seeing this in a VM, but on
baremetal.
If I downgrade to systemd-242-6.git9d34e79.fc31 the problem goes away.
I started a thread upstream.
https://lists.freedesktop.org/archives/systemd-devel/2019-August/043231.html