I don't understand how this is different in any way from bands which employees are placed in based on performance? Im not trying to be combative, I genuinely do not see how this would realize any different outcomes. It just seems to shift definitions around.

If employees A and B both are in the same band, both do not get promoted in a year, but have different performance ratings, I assume they will end up with different 'performance based pay' raises. Where is the difference to moving them to a different place in the band?