>If I read the online WSJT help files correctly, the wizards of WSJT indicate that in FT8 Contest Modes, appending the /P suffix will suppress transmission of the 4 character grid locator in the "CQ" message. If a country's regulatory agency requires that location data be sent when an amateur station transmits using FT8 mode at other than the operator's permitted location, the operator can't also append the /P suffix.
It seems that you got it wrong, it is other way round. Actually it is very easy to test what happens. Just type in Settings – General into My Call: whatever you need to study. E.g. to test whether OH3MA/P is supported I type it in and I will see immediately on the main screen
Note that none of those is supported with non-standard call signs such as OJ0/OH3MA/P.
73, Reino OH3mA