It’s been on the website and other places that it’s available for all resort guests, FWIW.
Somewhere along the way the powers that be opted to make the BLT pool BLT only, I’m guessing based on some room count ratio or other operational reasons, plus the fact that it’s largely hidden from hotel guests. Legally/technically, the BLT pool is a common element owned by BLT owners so maintenance fees pay all operating costs. Since BLT guests can also use the CR pools BLT owners pay a pro rata share of CR pool operating costs in their MFs.
The Poly pools, including the new Cove Pool, are owned by Disney, Disney passes through the pro rata share of costs to point owners. I’m assuming/guessing given the very close proximity to a number of hotel rooms and the fact that the Tower was added to existing DVC association, they’ve opted for this setup rather than exclusive to just DVC. The mechanics of that would be very messy in my opinion - three longhouses of Villa guests on the other side of the resort would have to have access to the pool but not 2-3 longhouses of hotel guests looking right at it. A PR and operational mess!
I’m sure the DVC pros will chime in with anything I phrased incorrectly in the above.