One and the same.
Waiting though revokes their advantage of first to market figures. Not all figures receive such drastic alterations from week to week. Considering this it's more damaging to wait than it is to publish using a baseline data set. Wii Fit specifically has had a very imbalanced distribution channel. Some stores received large shipments while others received very few.
Some titles just get odd distribution routes from D&H, Jack of all Games, Ingram, Mecca, etc...such that retailers VGC doesn't get initial data from could get second shipments faster or simply ordered more product to start with than average. International distributing is even more off the mark.
Besides NPD also changes their figures after initial publish as well. The difference is VGC readily admits it will update sales as new data is received while NPD very rarely publicly acknowledges their alterations.
The rEVOLution is not being televised
