Really??? Do you realise how quickly I can learn pieces just by listening to an audio file of them??? I'm incredibly sure that I can learn pieces faster, just by listening to them.
It's actually quite beneficial in fact.
And any pianist who is adequately schooled in solfege has an even better advantage than a pianist who has perfect pitch but has no education in solfege.
Perfect pitch tells you only the pitch at hand, not its context. Sure if you know the pitch and the one you're going too, you can work out that it's a 6th or what have you, but solfege teaches you to recognize the interval itself, and also mode/tonality, whatever.
THAT skill is useful, much moreso than perfect pitch, and is one that can be developed.
These are things that one can address of their own accord (buying a book and training oneself in solfege) or through being taught. At most music schools, solfege is a requirement, but it's never too early to start training your ear.
Perfect pitch is a nice trick, great for vocalists, but i wouldn't say it gives a pianist any advantage over another pianist. I know pianists that have perfect pitch, and I've never felt any disadvantage because I practiced my solfege and worked hard to develop my ability to recognize things. This ear training combined with adequate musical theory training is what's important.