An OTG product must have a single Micro-AB receptacle and no other USB receptacles. An OTG cable has a micro-A plug on one end, and a Micro-B plug on the other end
Micro-A is apparently similar to the standard Micro-B plug, but without chamfered corners:
A Micro-AB receptacle is also rectangular.
However, in practice, all of my phones that support USB OTG have Micro-B receptacles, not Micro-AB. And the OTG cable I have it front of me has a Micro-B plug. Also if you google photos of "OTG Cable" they all show Micro-B plugs
In fact I can't remember ever seeing a Micro-A plug. Is this something that Wikipedia has totally made up? Or is it something that is in the USB spec but the entire electronics industry wisely chose to ignore?