Well there you go, never read ICAO Doc 4444 so I stand corrected. I presume it being an ICAO doc it is a SARP (Standard and/or Recommended Procedure). This does not mean that all regulators require or indeed request it, as ICAO is not a regulator in its own right.
I have to say tho the mode C check is not done very often in civilisation, either that or I am not paying attention (can I use fatigue as an excuse).