DrDamn I kind of do and kind of don’t agree with that assessment.
I feel they negate the initial difficulty level by only requiring that you reach the bottom (no timer) to begin with. It’s only once you’ve descended once that the time attacks are unlocked for that level.
Also, when you start to understand just how big the shortcuts can be, and many aren’t heavily telegraphed, then those checkpoints get very very close together.
But it’s not obvious from the first hour or two of play, granted.