I know - they shared the library with me yesterday that Limor had produced a couple of days prior.
It is (or was) a little known capability of the PMS5003 that it can do both UART and I2C - Plantower only marketed certain models as I2C, not including PMS5003 at the time.
Problem is that library is a no go for Enviro+ FeatherWing. I’ve had a lot of interaction with Adafruit on this point, but nothing from Pimoroni.