This is my experience in using a USB OTG between a phone and SD card reader.
I wanted a simple way for my wife to transfer camera pics (SD card) to phone for social media while she was on holiday.
I purchased a Micro USB to Micro USB OTG Cable - 10 / 25mm SKU: ADA3610. It would connect between the phone and a USB Card reader we had. But it did not work.
I then purchased a cable similar to Micro USB OTG Host Cable (for Raspberry Pi Zero) SKU: CE04761 and a card reader with a standard USB connector and it worked perfectly as OTG.
This got me wondering why the original cable did not work. In my investigation I found that pin 4 ID pin of the micro USB connector must be GND for the phone to switch to host mode and read the SD card. The first cable has no connection to pin 4; the second cable did.
When you think about it, the micro USB to mico USB cable could not have pin 4 to GND for both ends. Both devices would try to be host. If only 1 end was GND, it would need a label, which may come off … etc etc etc.
The other cable is perfect for OTG as it can only be connected one way.
I relate this here in the hope that someone else may benefit from my experience. The google information I found did not explain specifically the connection of pin 4 to GND causes the phone to switch to host mode.
Core Electronics should add a note to the Adafruit description of the cable to state that pin 4 is not connected to GND. The cable can be used in certain situations to connect two USB micro devices but not when it is required to switch a phone or tablet to host mode (OTG). It is not the right cable to do this.