I think what was essentially 2 copies of the game in one package was a reward enough. The buddy pass was a fully-featured game code so anyone using it in 1.0 is still using it now and possibly has legacy bonuses and other stuff.

The whole point of the current program is to get people into playing this version of the game so I don't think the old should count if they even have any way to determine which is the "inviter" account and which is the "invited" since they were just normal registration codes.