You're misunderstanding him. He's not talking about him not having been traded at the deadline, he's implying that the flimsy case he made is writing on the wall that Stanton will not be traded.
That's what he has cared about most his entire tenure as an MLB owner. I don't know why that would surprise you or why you find it unlikely. Absent the year that he spent money on FAs after hoodwinking the city of Miami into building him a new ballpark (to the tune of $2.6B to the city), he has never spent real money on a free agent and never resigned one of his own upper echelon players. Oh and in case you missed it, he immediately traded all those FAs he signed at the end of the season.
There are many possible reasons why BC chose the deals he did and most of them have nothing to do with Stanton. First, as you say, Stanton will cost at least a couple top 5 prospects (not the packages you suggest but still). BC was not getting prospects back for either Lester or Lackey that would fill the slots of X, Swihart, Betts or Owens. So "stocking up on prospects" would have been adding more mid level talent, which the Sox have plenty of. I assure you that if the Cardinals offered Tavares for either guy, Ben would have taken that deal. He took the best deals on the table that served the overall future of the Sox the best.
Further, he saw that the offense needs more than Stanton. If they had traded both of those guys and taken every prospect they got and acquired Stanton with them, he still had work to do. Stanton alone wasn't returning this team to the top offense in baseball. Nor did the acquisitions preclude Stanton being on the team in 2015. Craig in LF, Cespedes in CF, Stanton in RF for a year until Nap is off the books, with Vic as your 4th OF, giving Betts another year to mature in CF in the minors and JBJ can now be included in the package. As an example.
No, Exhibit A is not the A's. They went all in on a season in which they have the best record in baseball, the best offense and a top 5 pitching staff. Shark has another year of control, so if the A's don't cash in, they can shop him in the offseason or keep him and shop him at the deadline next year to recoup a significant portion of what he gave up.
No one forgets the Cubs have payroll ability. That's not the point. The point is they have a shit ton of great offensive prospects and no pitching. If they trade from their wealth it will be for a pitcher. The Rays don't have close to the farm system to acquire him (ignoring the lack of common sense to suggest them in the first place) and the Twins and Astros are both well more than two years away from contending. \
And not everyone is saying he will definitely go to the Sox. The reasonable people here are saying that all logic points to him being traded sometime in the near future and the Sox offer the best combination of want, need, currency to acquire and ability to resign.
If you assume he wants to go to free agency, then you undercut your own position that Miami would keep him. They are not going to let an asset leave for nothing more than a comp pick. They have never done this in their history. As MakMan said, no one is trading for him without a window to discuss an extension.
It is on the wall, you just don't seem to be able to read it very well.