Wasn't the issue.
In PG1, my units from '39 could take Poland, France, the early blitzkriegs, then choose to go to Africa (or Russia), then pop back into the mainland European campaign afterwards and get in the full war.
In this expansion, I can do the Afrika Korps expansion (which, by the way, is playing out like a very linear story, from my perspective), but that's that. No pre-Afrika or post-Afrika participation for my units, from what I can tell.
This expansion, IMO, leans more towards PG2 than PG1 in design. Lots of "smaller picture" scenarios in sequence rather than the sweep and scope (and options) of PG1.
Some will love this expansion. Personally, I see it as an entertaining once-through sort of experience and cannot see playing through it twice.
However, I do look forward to what Slitherine can do with an "Allied Corps" type game, and hope they keep the focus a bit more strategic and make it a '39 - '45 experience ('42 - '45 for Americans, of course.)
Playing Africa as part of a bigger thing is cool, but at the same time you miss some interesting opportunities, like using italians as proper members of your core. I agree that it is a question of taste, but for us it was not an option to release AK expansion as a couple of scenarios extending the main campaign. From an expansion like this people expect to get a lot of hours of gameplay, which only a big campaign can provide. And no, it is not closer to PG2, simply because the scale is still PG1-ish. Many AK scenarios cover entire countries, culminating in India. It is still a grand scale campaign. As for branches, PzC experience has proved that they do not improve replayability of the game for 90% of players. They just play the primary victory branch. You are free to disagree, but it is a fact. Hence our decision to concentrate on this primary branch in AK. However, it still includes alternative branches for people who like to make choices, or take an occasional defeat in order to go down the historical branch, ending in german defeat.
We might think about extending main campaign with a few Africa scens in a free patch, or when we get to Gold version of PzC, but this is a thing for the future.