Funnily enough, this came up in a similar comment earlier today.
https://news.ycombinator.com/item?id=23319868
It's important to note that Qt is only talking about the commercial LTS release, and not the open source version of Qt.
All development of new code released in open source Qt is still released in the development branch, the open source community 'misses' the back ports into the stable (LTS) branch.