It is true regardless the game plan, you need ypur lines closer to each other. One element always affects the other. You press high, you must have a high line, otherwise you leave more space in midfield. You sit a bit deeper, you don't press higher.
The main thing is to be compact as a team, midfield trio does only half of the job, the second half is done by the other two lines. One extra midfielder won't make that much difference if minimal changes are done in defense and attacking approaches.
Even if you have a high line if you constantly press absurdly high... the team is longer than ideal, unless you put that line at halfway line. Which is not recommended in the first place.
PSG is simply smarter than us with how they alter between pressing and compact defending. They will often press more when teams are more tired, many better variations on tactical level.
Arsenal are smarter too. Another team that would switch between different approaches super fast.
They have better players obviously, but there's more to it. Also worth nothing that the best Liverpool under Klopp was with 3 hard intense players in midfield. Henderson, Fabinho, Milner. Ball winners, hard defenders. Not a playmaker in sight there.
Flick is unfortunately overly ambitious to the point of naive. There is always a trade-off involved. Everyone said how much better Klopp Liverpool would have been with a better midfielder on the ball, but players who are better on the ball, or very creative, come a cost in other areas.