It has dropped down the list of priorities, but it is still an issue.
Surely these can be recovered, even if you didn't retrieve them properly when removing managed iPads, the licenses shouldn't be gone for good, you organisation owns them, I have never seen that warned anywhere on any MDM.
Meraki's guides on this focus on VPP users, not VPP licenses/Devices.
I had the same issue and the following worked for me. In the app listing, I clicked on "Revoke unknown device licenses" and "Refresh details" and then I refreshed the page and my license count went down and removed the devices that I had deleted. I'm not sure which one of those actually did the trick, but it worked!