Well, if this were plausible, you would expect to hear a lot more complaints from people who live and work near datacenters. But we don’t, so I think it’s pretty easy to conclude that these computers aren’t emitting ultrasound, or if they are that it isn’t the source of the issue.
Do you know how loud ultrasound has to be just to travel a few meters through the air? People would basically have to be living inside the datacenter even if these things were converting half their energy input into deliberately generating ultrasound.