The big problem with retroactive point-giving would be that it would cause chain reactions of rating changes.
Indeed, suppose player A was beaten by player B who cheated, which is reported a month later. But during that time (after his loss and before the reporting), player A completed several games against player C, D, etc. If you change the result of match A-B, then A's rating would be different when he completed the game against C, D, etc. Then, you have to change the rating adjustment of those games, even if the result is the same. But then, if C,D, etc. had completed games between their game with A and the adjustment etc...
You wouldn't like your own rating to be decreased because lately you won against someone who drew against someone who lost to a cheater, would you ?
Not changing the points, although it sounds painful to be beaten by a cheater, is still IMO the best way to go.
What if the player caught cheating after he won the game on team match. Will the points be given to the opponent or not?
I have seen this in one of the team match I'm in and there's an opponent who won 2 games on the match and get account closure.
Any comments?