The point of the IW/Gardens rush is just that, it's a rush. Your goal is not to amass a ton of points. Your goal is to end the game ASAP. This game lasted 28 turns. Sure you got your gardens up to 7 points, but you know, Colonies are still worth 10. And draining colonies in 28 turns is not that hard to do, especially with a fantastic card in masquerade.
There are basically 2 ways to do the IW/Gardens rush. One when you are both doing the rush, and the other when it's only you. When it's both players, yeah you want to start in on the gardens pretty soon and you dont need a ton of IW. This is because, you need more gardens likely to win. If you aren't contested, then you need to drain 3 piles all by yourself. In this case, get a lot more IW (or workshops) before going in on the gardens.