Judging by the posts here and on the CAG front page, this seems to go in and out of stock fairly frequently at BB (much like the SSB Ultimate CE). You have to be online at the right time and hope for the best.
I'm going to go ahead and disagree with your conclusion (even if the evidence seems to suggest otherwise).
I've been carefully tracking the BestBuy SKU since I missed the original ~15 minute window due to dinner (priorities, right?). Yes, the preorder button has cycled over the past weeks, several times when I've been sitting at the computer. According to the data I've mined, the SKU appears live for either 7, 14, or 21 minute cycles; I have not been able to determine if there's a functional difference between them, at least from my perspective.
When the SKU goes live, you can add the item to your cart - it's the checkout that's problematic. I've personally had the item in my cart since a day or two after the original listing and have never gotten one step closer to checkout. Neither shipping or store pickup seems to make any difference, and that's even when the link goes live while I've been at my computer, doing a random 20-second cycle of F5ing when I happen to have a moment to check.
The only conclusion I can draw is that, if these preorder links are truly 'live' is that BestBuy is somehow gating customers based on geographical location. For example, if a user in California were to have secured a preorder, then cancelled it (one of the ways that inventory goes back into central BestBuy stock), only nearby users in California would be able to checkout from the newly-reinstated preorder link.
The concerning part (for me, at least) is that this would run counter to past BestBuy practice/policy on limited stock, highly-desired, preorder items. I've had pretty good past success nabbing limited stock preorders for 'hot' items, like NES/SNES Classic, FE:Fates SE, among others. Normally, if you're the first to try and checkout, there's no problem. However, this item is notably different and I've NEVER had a situation that's literally taken weeks, without even any close successes.
Don't get me wrong, I have one secured through Amazon and, now, Target, just to make sure that I get at least one copy on release for my own personal collection. For me, BestBuy simply allows me to take advantage of my final 9 months of GCU and is a direct cost-savings. That, and BestBuy store pickup usually removes the uncertainty of damaged goods in bubble mailers, etc.
I'm also starting to think that this item won't be especially rare, more akin to the FE: Shadows of Valentia SE. As a new title and the first on the Switch, I don't think it will be 'as' abundant as the Valentia SE...but not nearly in the FE: Fates category.
