Catalyst provides alternative pathway to the reactants. Does it also mean that the potential energy surface is altered?
As you said, catalysts do not alter the PES, but extend it to other dimensions, which usually provide new reaction pathways with lower reaction barriers. If you consider a surface catalyst and an impinged molecule. Considering the full systems PES, the pure molecule PES is a part of it (for large distances of the surface to the molecule). If we bring the molecule closer to the surface, we get new partial PES which have lower reaction barriers.