I agree with this assessment in general but I think things might be shifting. I'm guessing that they aren't getting as many reservations as they want, maybe even holding back at times to make demand seem higher then releasing spots so people feel like they're lucky to get in. I got an email the other day from Disneyland "reminding" me to make reservations if I want to go, which felt like a push to get more people to go. You wouldn't think they'd do that if they were selling out as much as they wanted. Especially as capacity continues to ramp up, existing tickets are used up, and people get their fill on full price tickets, it wouldn't be too surprising to see the demand start to fall and dates open up.
Would Disney cut off reservations even if they weren't sold out the day before to make demand seem higher? I wonder. I do know that for March 13, 2020 (last day before closing), flex pass reservations were sold out, but the parks were pretty empty. I think they pretty clearly cut those off to keep crowds down. I have to wonder with the wait times and reports of empty parks in the evenings if they are really selling out all these days or just saying they are to avoid the appearance of falling demand. They couldn't really maintain all these full price ticket sales if people realize that fewer and fewer people are going for it.
Just my thoughts on the matter.