If you fly into Nice you'll have come across this one.
The Papi's on 4L are set for Cat D aircraft. So if you are in a shorter aircraft like a 737-600 you will fly the ILS perfectly and the papi's will be 3R/1W.
As someone said before this is a function of the papi lights being deeper.
Therefore the 2W/2R at Nice would land you deep if followed in anything shorter than the 747.
Aéroport de Nice Cote d'Azur - FAQ, Saleya, PAPI