CircuitPython 7.2.5: tested on FeatherS2 and Adafruit Feather ESP32-S2. Also true as far back as 6.3.0 (did not test further back).

Using the PCA9685 driver, there is at minimum an almost 10ms gap between any two I2C transactions. This causes stepper motor rotations to be very slow, etc. This slowness was first noticed by a user here: https://forums.adafruit.com/viewtopic.php?f=60&t=190046.

I see a similar 10ms gap in some case in the SHT4x library, so I think it is generic to I2C.