I was initially going to respond it might be because pixel 9 has a ultrasonic sensor, and that the ultrasonic pulse probably can 'penetrate' the specific glove if it works. However, a quick search on the net brings up results from people experiencing the same behavior with some latex & nitrile gloves on phones having an optical sensor, meaning the light from optical sensors can 'penetrate' some specific gloves aswell.
So nothing to worry about in that sense, however quite interesting, i learned something new today.