Are new apt packages still being released for debian stretch?

Hi,

How do the apt package releases work? I see that the apt package for debian
buster is version 2.29
(http://downloads.skewed.de/apt/buster/dists/buster/main/source/ see
Sources.gz), however for debian stretch it is still version 2.27
(http://downloads.skewed.de/apt/stretch/dists/stretch/main/source/).

Thanks,
Manuel

Stretch is too outdated to compile current versions of graph-tool, which
require a C++17 compiler.