I assume that's because the IP range of your company network overlaps with a range used by some scrapers, and if it doesn't happen on your phone even in the corporate network, then IA probably checks some extra signals like the user agent in addition to the IP
No - my phone is not connected to work's WiFi.
Wonder who the bad actors in my company are...
There are definitely factors beyond IP being used. A week ago I found that all requests from Chrome-like browsers got a 429 across more than a half dozen networks and several machines, while Firefox reliably worked. I assume this was an overzealous policy on UAs.