I don't work for AC, and I'm certainly not an AC apologist, but as a product manager in the software industry I can state with some confidence that the above is likely incorrect.

Unless we work in AC IT we really have no idea what the level of effort would be to implement this, nor what the cost would be in terms of IT development cycles.

It's not like these systems change through the clicking of a few buttons.

The software managing seat assignments is likely extremely complex, and a change like this would likely require many hours of QA work to ensure nothing got buggered up.

...and to my mind it's moot anyway. Every AC flight I'm on these days is 100% full. (Granted, I rarely fly the triangle.)