You can certainly argue that policy has been changed, and to a casual observer in particular it definitely looks like we have units in a lot of ways. Which is fine. However.
1. In terms of game code, we only have one thing: buildings.
2. From a practical standpoint, "units" cannot go and stand on top of buildings.
3. The saucers behave exactly like any other building, with the added effect that they can move periodically. To me, this is more akin to having a military base that you pick up and move, rather than specific soldiers. But we're splitting hairs there.
4. One way or another there has to be a system of positioning, and that was always intended to be with mobile military bases. On the player side that was being hampered by the AI shooting first and getting you real quick before you could establish anything in range. With the new system of international incidents, that's no longer the case if you are acting preemptively. And if you're not acting preemptively, you can deviously request a ceasefire temporarily to do so.
5. On the AI side, that sort of positioning and whatnot would be an incredible pain to code and manage. It would take us a lot of time, plus eat up incredible amounts of CPU. The saucers also look nice and intimidating since you don't have them. So letting the AI's mobile forward bases be actually mobile buildings made sense to me.
The TLDR: I don't personally see this as a policy change, but rather a concession to the practical needs of how AIs set up their mobile forward bases. Looking at it from a more distant point of view, I could see the argument against this in terms of the grand design, though.
