Maybe he meant this
That would be for triggering card insert detection.
For most of 8bit board like RAMPS 1.4, it would just reboot the board when an insertion event was triggered. So that, if you use this kind of extension cable, it won’t trigger that event
Anyhow, on P1S, the uSD card is simply just like drive C on your PC, you can only remove it when powering down the printer.