Note that this question is also being discussed in the FIs & Examiners forum as the C172RG in question is being used for FI training:
POH C172 RG
Copying part of my response from that thread: Cessna may have put the text there to protect against the 'typical' early 1980's GA pilot, someone who may have trained on fixed gear types and is prone to forget the gear handle is there. Especially as 98% of the C172 fleet doesn't have a gear handle.