Normally I would agree, and make no mistake, all things considered, it is a bit irritating to see a promotion like this one. However, I will have to agree that this is simply another example of marketing doing what marketing does.
I look at it like this; If I buy a game day 1, that means I am the early adopter, and no matter what that wont change. If 3-6 months to a year down the line the game gets a discount in the store, or is added to say Games for Gold or Gamepass at a discount, I dont just get a refund. Could I have waited? Sure but then I would have missed out on things that only those who HAD the game early or day 1 have. Its a balancing act, and sadly not everyone can be balanced evenly. (The community is just too big). This applies to many things, not even just games. There are always incentives to buy a game early, and there are always incentives to buy into a game late, and in-between those two there are distinct advantages and disadvantages to both groups.
I WILL add however, that considering the Controversy and Drama that ensued prior to this sets release (I wont go into that here since its an Insiders thing and I am not sure how much can now be talked about now that its released, but I am not going to pretend it did not/is not still happening in other areas that do NOT include Insiders), that I am more inclined to agree with you in THIS particular instance (Hopefully you know what I am referring to since your also on Insiders). It feels like another instance of RARE not quite paying attention or listening properly to its playerbase. It is ONLY due to those mitigating circumstances that I support your premise with THIS particular promotion regarding THESE particular items.
(To be clear, I would probably NOT support your position if it were under different circumstances with a different set of items, but I am being broad as there are certainly other instances where I would support your position.)