No, that doesnt really make sense.
Can you quote or link where you've seen that?
What they may be talking about is DX10. That card is capable of running new games with DX10, but only Vista will have the DX10 upgrade.
If you have XP the video cards and games will still work, It will just lack the features DX10 is capable of. XP will not get a DX10 upgrade.