Okay, I do recall that our software had a feature that could classify on "DHCP requested options’, but it was low-fidelity, unreliable. Ultimately, the software works best with known devices, and isn’t very good at reliably classing unknowns.
As you say, just the first few seconds of actual traffic from a device is so rich in terms of ID characteristics compared to DHCP.
I was way off! I thought it was one of these:
I wish I’d had better capabilities when I took that photo…