My humble opinion, if you don't mind.
Actually, that's not news - Pep started to develop more 'vertical' version of his 'positional play' system during 2nd season with Bayern and has achieved significant results in his final year. He implemented more complex ways to invite pressure and then bypass it by 'large-sized' combinations, sometimes in the scale of the whole pitch. As I assume, the main catalysts of that step were:
1) regular encounters with well-educated German coaches playing on counters in every game with Bayern (the average level of coaching there is incomparable with that in England IMO). Pep just had to find an antidote (or you could call it 'plan B') for deep-sitting teams.
2) particular abilities of his Bayern players. After Schweini's and Kroos' departures their squad became short of players able to play short-passing game in tight spaces under pressure. Thiago hasn't proved himself as an intelligent, 'strategic' passer, and the purchase of Vidal last summer has completed this trend - Bayern's board clearly had its own view of the ideal squad (I don't criticise them, it's their business, just notice that it forced Pep to adapt, learn and try things that were entirely new for him). Pep had to find a way to break the walls without skilled 'dwarfes', relying more on the speed & physical power.
What's entirely new for me is the combination of that bits with 'Barca-style' small midfielders/attackers and the middle-focused play (Bayern relied more on the wingplay) which is clearly seen in City's play now. Basically, Pep is now taking the best parts from both systems and fusing them together (I know it sounds too simplifying, but that's how I see it).
Idk where this will lead City in terms of tactics in 3-4 years, maybe even Pep doesn't know that exactly. His work is an endless experiment using trial-and-error method.