I just shaved a day and a half off my time to learn Master Gardener by buying two of the "Increase by 1" cards. And, it should work now for everyone, and on all new skills going forward.
HOWEVER, I also bought 3 cards on the weekend and those didn't count and will not — ultimately, there is no way for us to know what the BC was before the skill started being learned and how much it was sped up before, and whether it was paused, etc. — this fix only applies to newly purchased cards.