OK, how about things like the Apogee Jam[1] and MIDI adaptors? As far as I can tell, there aren't any MFi-certified Lightning splitters that support both data IO and audio out. (Usually it's just audio out + charge — and poor audio at that.)
Well, how about them? That's a reasonable concern, and a major problem for people who want to use such devices with an iPhone 7. They aren't Square readers, though, or any other kind of device that uses the headphone jack for data, and it's inaccurate, disingenuous, and unhelpful to claim that such devices no longer work.
[1]: http://www.apogeedigital.com/products/jam