Which is erroneous. If you can get the game cheaper than at launch, certainly go for it - but then that same consideration applies to getting the game at any point post-launch before it's first on sale; whether you pre-order it or get it two days after release makes no difference, and usually games offer a small discount for pre-orders which makes them cheaper than they would be for some months afterwards (Rome 2 did this, for example).
As for waiting until it's patched up, again this applies to day of release and later, but beyond that it makes the false (and frankly bizarre) assumption that somehow, if you preorder the game, you won't benefit from the same patches as everyone else. Anyone who preordered Rome 2, for example, is playing the same game today for no greater financial outlay than someone who bought it yesterday, since the game's base price now is no lower than it was at release.
Of course, if the game is bugged at release the player may be put off trying it again post-patches, but that's their choice and again has nothing to do with preordering.