I highly recommend that people learn ETRTO as it helps make sense of the remnants are the various European systems out there.

28in and 29in is still very commonly used in multiple countries (on trekking and MTB bikes in Germany as an example) and is simply a 700c in France. ETRTO clarifies all of these into a simple -622.

I like the romance of calling a 650b and 27.5 but it gets confusing cycling across multiple countries where those archaic systems mean different things.