Also big nitpick here: gray market has a specific definition and this author misuses the term. The sellers he refers to are not necessarily selling gray market products. Another inaccuracy is that you win the buy box by having the lowest price. This is not true. Any experienced Amazon person could tell you that it is a blend of price, fulfillment method (prime or not), delivery latency (is this offer for a product that is in a warehouse physically close to you), and seller feedback rating.
SBA is actually a good idea from Amazon and they even put in some volatility protections for people who enroll. It is also a good alternative to the Vendor program with some of the benefits without some of its headaches.
If you look at it from the perspective of it being a better alternative to Vendor for some brands, it makes a lot more sense. It is not pitched to conventional sellers who stock tons of brands. It's pitched to brands who want to sell direct to consumer on Amazon. Historically Vendors have also gotten the kinds of indirect marketing benefits that are being pitched to new users of SBA, so even that is not actually a big change.
For example, Vendor products (those shipped and sold by Amazon.com) have always received a massive buy box benefit even if the price is not the lowest. In the weighted buy box system Amazon has always assigned itself a massive bonus score. So in that there is not much that is changing.
Naturally, "incremental bureaucratic change pitched to brands as a middle ground between two existing bureaucratic programs at gargantuan mega-company pitched to other faceless corporations" is not that interesting of an article. This type of opt-in program would work for a very specific type of company and isn't really indicative of a big upcoming change of how the whole thing works.