If you are just a gamer, why would you like to know 'corporate' reasons? Sally clearly stated in the OP that they won't discuss any instancing situations here, they have the right to keep technical and/or marketing reasons for insiders only.
I just can't see the problem here, lets say your 'squadron' consists of 15 friends; if 10 of them already own Odyssey, given the other 5 just tested AND LIKED Horizons 4.0 and it runs fine on their machines, they can simply buy Odyssey (or the other 10 can gift them Odyssey if some can't afford it, you're friends after all!), problem solved. If, on the other hand, the 5 non-Odyssey owners, can't run Horizons 4.0 decently on their machines, then all the group can join in 3.8 as always, problem solved. Easy as that.