You say its a work PC - are you an administrator on this machine? Enterprise machines have often (for over a decade) locked the USB port so corporate data can't be copied off via USB.
I've seen USB drives show up weirdly on such machines.
What do you mean by "like an Android file system"?
Was this drive ever encrypted? That'll make it show up weird too.
The only other thing I can think of is there's something odd with that adapter.