From the PkHex Thread, I asked the same question:
Sorry Kaphotics, I forgot to mention that I do not care about bypassing online checks or anything like that, I'm only interested in why the new PID cheat code from Powersaves actually edits the IVs. Actually I'm a hack checker in a german pokemon forum, so I take the pokemon from users that need my help, partially decrypt the PS backups and then view the result in PkHex. Since pokecheck is down it's the best option we have to keep away hacks. If you want me to verify me I could easily do that, but I hope it's not necessary. So it's not a question about bypassing checks, it's more about identifying hacked pokemon. If it is the case that the PID is connected to the IVs again and we'd know the algorithm it would be easy to identify hacked IVs, wouldn't it? Hope I don't ask too many questions, but I'd be great if you'd be able to explain, why powersaves acts this way.