No, it is not and it never was... The same player does not "worth" the same on diferrent surfaces and his current ranking does not reflect his current form.
Some poeple are quick to jump and "find" a loophole in the system. However, only few are able to give a constructive feedback and evaluation of it.
The system is not meant to distinguish the surfaces point wise. Not even current system make difference point wise!! If you know the system that would be able to value a player per surface, please come up with. hehe...I no need a smilie for this one.
The idea of the "system" is not to reflect current form of a player. His ranking position is to value his point "weight".
The whole idea is, which you didn't get, to differ award for someone who beats Nadal (the #1) and someone who beats Tomas berdich (the #20). The reward must not be the same. Since the effort is not the same.
Whether it is on clay, concrete, grass or brick, it doesn't matter. Since it's not all depending on one single match nor on one single tournament! A tennis professional suppose to play more than just few tourneys anyway. The GS-s have all the same amount of ranking points in total regardless of the surface.
If you want to differ and value players by surface, fine! Go ahead and figure that ranking system. I am sure many would be thankful to you. Me first.