Your voice should thin down as you go up in pitch. If it doesn't, then you need to learn to do that, because we can't sustain as much low tone as we do in chest voice when we go up higher.
That is called "shedding the weight". When we get up higher we sing in "little boy voice" or "little girl voice" to accommodate the required "smaller" tone.
So yes, you may feel that as different "layers". Ken talks about this in the videos, sometimes using the metaphors of "an elevator going to different floors" or like a Rocket, using the big booster stage to start getting off the ground down low(Chest), then firing the second stage (mid voice), then firing the third stage (head voice) to take you to the top. These processes are reversed when you go back down scale, and you restore the lower tones gradually as you descend in pitch.
Besides the shedding of weight, there are also vowel modifications that naturally occur as the voice goes up in pitch. We have to learn to allow the modifications to happen or we will try to keep the vowels static. AH becomes Aw, then oo, then Ooh, for example. When we let the vocal tract change to allow the modifications, it helps to allow us to sing higher with less stress. The sound is a little different, but it is actually the natural sound of that vowel sung by you at that note. Let that happen and your voice will naturally grow and experience healthy singing.
We learn to smooth these processes out and try to seamlessly join the different stages, floors, or layers of our voice into one long, smooth, continuous voice.