I agree, but at the same time, I disagree.
None of the WPs in the WP Shop that can be aquired within the first three points are anything that can be abused to the point where a new rule, or addition to game mechanics needs to be made because of them.
The only thing that could be "abused" would be the spells in the later parts of the Shop. The B/W Joker isn't going to make anyone over powered, and they aren't exactly worth much. The GG Drach > Windy WP isn't accessible to REALLY late in the shop.
This achievement will only lower the value of WPs, but at the same time, this is MAGIC DUEL. WPs shouldnt be these incredibly hard things to aquire unless you're friends with the right people.
Players should have SOME basic spells to play around with. It's the point of the game, right?