The FCC says it's safe, and as the transmitter frequency band is the same as used by cell phones, baby monitors and your home WiFi system, and the transmissions are in a burst only lasting between 12 and 120 milliseconds, I would tend to believe them.
But we do if they are uninvited ;)
In my youth I had sold cars and motorcycles to people who has promised faithfully to make payments.
Having learned from those costly lessons; never again.
I don't think people have changed for the better since then.
I understand, but when I was working with the PO's here, we would not have a friendly chat on the doorstep before deciding to search.
We would go straight in because we didn't want to give them the opportunity to dispose of anything.
Perhaps the OP can tell us if anything was found during the...
What reason did the probation officer give as to why they wanted to search the house?
Your statement that the probationer was being interviewed at the front door could lead someone to believe that the PO saw or smelt something in the house that justified a search.
It may be moot judging by how many flights from Japan to the US have been suspended and I believe that only US citizens are allowed to return.
As a precaution it would be wise to make alternative arrangements to have your baby in Japan, as your partner may be unable to get any sort of visa...