It's not about the APC40 specifically, it's about using faders or rotaries on a midi controller for this in general.
Why don't you give it a try? Map your first fader to this control on layer 1, and then try to accurately trigger clips with it. Pretty hard to do, right?
This feature is more intended for use with for instance Ableton Live or Vezer. Before, if you wanted to sequence clips from an app like this, you'd have to go back and forth and assign a Midi Note for each and every clip you'd want to trigger. It's do-able, but pretty mind-numbing.
Now, you can just assign a single CC to the layer, and then sequence by drawing envelope values for that CC.