Is the expectation here that firms offering software under non-commercial-use-is-free licenses just run it entirely on the honour system? And isn't it true that many firms use unlicensed software, hence the need for audits?
They can also apply stronger heuristics, like popping up a dialogue box if the computer is centrally-managed (e.g.: Mac MDM, Windows domain, Windows Pro/Enterprise, etc.).
The (commercially licensed) Extensions pack provide "Support for USB 2.0 and USB 3.0 devices, VirtualBox RDP, disk encryption, NVMe and PXE boot for Intel cards"[1] and some other functionality e.g. webcam passthrough [2]. There may be additional functionality enabled by the Extension pack I cannot find at a glance, but those are the main things.
[1] https://www.virtualbox.org/wiki/Downloads [2] https://www.virtualbox.org/manual/ch01.html#intro-installing
With my MBP as host and Ubuntu as guest, I found that VirtualBox (with and without guest extensions installed) had a lot of graphical performance issues that Fusion did not.