I found this article far more interesting than expected!
It seems like the way P2P is handled resemble how the programmer (yes, one person) first tried to make CMBO(i) work in "online" mode, in order to keep data transfer to a minimum (ii). Initial tests were promising, but as soon as they actually tried to run the game using two computers that weren't the same make and model things went bad. With the way different CPUs handle rounding errors and such the outcome of a turn could end up quite differently on the two computers. Wonder if that apply to For Honor as well?
Anyway, now that FH has lost so many players (which to me isn't that surprising given how repetitive, and thus boring, it looks) it's cheaper and easier to run dedicated servers than it was previously.
(i) Combat Mission: Beyond Overlord is an operational level turn based game that was developed by the two man company Big Time Software in the 90:ies. It was a great game, as indicated by the individual players spending hundreds of hours just playing the two demos released before the actual game!
CMBO's two next successors, CMBB and CMAK, were even better... (the third and later were, in my opinion, not.)
(ii) This was in the days of sluggish phone modems that made data transfer times an issue. The idea of having both computers "crunch" each turn simultaneously as a means to save waiting time was flawed from onset though. The time required to compute a single turn could differ way more between a fast and a slow CPU than the added time of transfer all input and output data instead of just the changes. Having all computing done on the faster CPU could literally save hours of waiting time in a game.