And surely there are tonnes of codes with R not referring solely to ramp... The purser said something in the line of "We have a HON and a Romeo..".

Clearly it was understood (now I know) that a wheelchair user was approaching the plane but could have meant something else. So, Romeo means wheelchair approaching the plane.

Why not just say "We have a wheel chair coming our way" or must it be so mysterious when we get to the airport-airplane?