I did a bit of digging last night.

Canonical can get some idea of usage, just not in the way people seem to think.

Mirror & telemetry data (aggregate, not per-user)
They can see things like:

IPs hitting mirrors
Package download volumes
Which releases are being pulled

Useful for trends and capacity planning, but it’s not tied to individuals or licences.

Optional telemetry (since 18.04)
There’s a one-off system report:

Hardware profile
Installed packages (high level)
Basic system config

You can opt out, and plenty do.

Ubuntu Pro (formerly Advantage)
This is the only place it gets closer to “counting”:

Machines are attached to a subscription
So yes, they can see numbers there

But that’s about support entitlement, not policing updates.