I had the opportunity once to talk to an IP lawyer for Oracle and brought this up. I specifically brought up the S3 compatibility of their cloud storage among other instances.
His reply was “without admitting anything specific, how do you know we haven’t purchased private licenses for anything you just mentioned?”
Plenty of good, cheap DACs built in China (e.g. Topping) have an HDMI-shaped plug (IIS) that supports PCM-over-not-HDMI which happens to be compatible with HDMI sources, but don't dare mention HDMI because they don't want to pull in an interlocking, price-gouging nonsense from the US entertainment industry.
So you don't quite need a license for the shape of the plug, but you do need to pretend it's not something that it is.
His reply was “without admitting anything specific, how do you know we haven’t purchased private licenses for anything you just mentioned?”