The Sonic Access music tracks do have the Holosync frequencies embedded.
The reason you want to have 20 minutes between listening sessions does not involve those frequencies, but rather the fact that when you are doing significant change work, you are working with shifting the entire paradigm from which you are operating. You need to let the energies of that new orientation settle in before you add something else.
It’s very akin to throwing pebbles in a still pond. If you throw one in, you can see the effects in the ripples that the single stone creates. If you throw in more than one, it’s hard to see what is doing what and that makes it harder to replicate and enhance what IS working.
All the best,