I2C-carrying STEMMA also has an GPIO and analog STEMMA counterpart, using 3-pin JST PH connectors for things like WS2812 strips – where 5 V compatibility becomes exceptionally handy. However ...

but it appears that Apple is changing the 3-pin Smart Connector on the iPad Pro. The site has little further information about the nature of these new 4-pin ports, but speculates that they may be ...