That doesn't matter anymore unless they have an SSL proxy. If you have ECH/ODoH anyway.

If anyone can fingerprint your personal device while literally inside the building, it is Facebook.

You don’t even need any to do something fancy in software. Could just be correlating mobile device presence with work laptop activity. Can triangulate physical location with a handful of Bluetooth or WiFi beacons.

Lots of those these days. Zacaler has a fair amount of enterprise market penetration.