While of course you are technically correct, think about it from the grandma perspective. Grandma uses $app that requires wine, but grandson set her up on Debian stable. She can't run the latest wine because it isn't stable, and it's needed for $app, without updating the system to unstable.

I could be erroneously attributing the intended use case, but I believe this isn't designed for people who know what they're doing; it's for people who don't know, like grandma.

I have some programs that it's ok if they are bleeding edge and unstable to get the most features. Some programs that is not ok. And if those 2 categories have a shared dependency (different versions of it), that becomes an issue.

I would say that most things should use the old model, but there are scenarios where this could be preferred.