Ok @stevesommars, the Raspberry Pi 4 has two usb2 ports and two usb3 ports. were you connected to usb3 ports when doing this test?
I understand latency in usb, but usb3 may have two mechanisms for accounting for these delays with (a) interrupt events rather than polling and (b) hardware timestamping.
So far nobody has been able to explain the favorable results from @Bas posted above on Feb 20 and Feb 22. It seems to be working with this particular device with PPS over usb3.