What do they mean by "checked"? Do they mean the fluid level or the chemistry?
Probably just a subjective check by an experienced mechanic familiar with the difference between good and bad fluid . In the past it was not uncommon to check the condition of engine oil by its colour and whether it still appears to be the correct viscosity. They might also also rub some between their fingers to see if it felt 'right' , or for any signs of grittiness etc. The same may still be done with the much more expensive CVT fluid.
Honda probably set the change intervals for the worse case scenario of city traffic, climbing mount Fuji etc. Many owners will be more gentle, with motorway miles, gentle runs etc putting less stress on the fluid and allowing longer change intervals. Even this relatively crude inspection would be sufficient to say if the interval can safely be extended . IMO.
The fingertip test is now discouraged due to medical risks but they might still do it wearing thin nitrile gloves .