RedHat shares IBM’s model of “change the terms and product definitions every year and audit folks to death who can’t switch providers”

They are going to irrelevance together.

I've worked with several large firms that had large footprints of Red Hat products and never heard about them being audited. You're confusing them with Oracle.

I worked for Cisco who were big RH users (RHEL, OpenStack, OpenShift, Quay, etc). We were audited and it basically comes up when contracts are renewed. It's not a bad thing, you just need to be honest about what you're using and how much and then just pay the man. Or don't and switch to other offerings. One thing I liked about RH is that they worked with you vs Oracle which was pure evil when it came being audited.

No, just sounds like that person can’t keep track of how many system they deploy.

Well, it's not always as simple as 'how many systems' even when you're talking about just an operating system. There's licensing based on cores and/or sockets. Then there's licensing for virtual machines.

Oracle was really nasty in some of the licensing scenarios, IIRC. If you ran an Oracle DB on an unlicensed platform in a VM (such as VMWare), then when you got audited, you needed to pay for how many cores/sockets were in the physical server, rather than just how much CPU your VM was using.

Is there evidence of Red Hat ever doing that kind of gotcha licensing?

I don't know of any, but that isn't to say there isn't any. Oracle on the other hand is widely known for this practice.