Experience only: Huge speed Boost after migration from 7.2 -> 7.4

[hellfire]

I just did an upgrade at a "active/passive" cluster with 60 virtual machines from pve 7.2 to 7.4 backed by drbd9 storage (=shared nothing).

• upgrade of standby node
• migration away from primary to standby node: about 3 hours or so.
• upgrade of primary node
• migration back to primary node: 46 minutes? WTF?

Coincidence?
Just difference in network saturation?
Considerable Improvements in PVE?