To put it in terms relating to Liverpool. In terms of defensive depth, imagine we have a flat midfield. If someone escapes a tackle from Hendo
Likewise Robertson and Mane in the other example.
No matter what the starting formation is. If it is a back 4, you will see the CB split and a midfielder drop in with them (City). Or one full back push up
This means picking your moments to press high, when you can do so as a compact unit
But the basic principals are drilled into him, thus he makes fantastic tactical