Out of curiosity, I looked at photos of the other Sheraton airport hotels in Europe. Granted, these are professional corporate marketing photos taken with wide lenses and such, but just by looking at how much furniture they can fit in the rooms, the rooms at Nice Airport definitely look smaller.

Paris: https://www.marriott.com/en-us/hotel...-hotel/photos/
Dusseldorf: https://www.marriott.com/en-us/hotel...-hotel/photos/
Amsterdam: https://www.marriott.com/en-us/hotel...center/photos/
Brussels: https://www.marriott.com/en-us/hotel...-hotel/photos/

Milan is probably the best comp as a modern Sheraton airport hotel, because the others were built in the late 80s and early 90s. The standard rooms there look quite a bit larger
https://www.marriott.com/en-us/hotel...centre/photos/

The only rooms that look equally small are at Frankfurt Airport, but that hotel was built in 1975.
https://www.marriott.com/en-us/hotel...center/photos/