No it is not a change in policy. The kernel sources for all the sony devices can also be found on the internet, maybe only published and maybe even maintained by the vendor.
Here we just see a massive dump done by jolla, maybe because the vendor does not care or dare.
A really bad sign if you ask me. Let us revisit in 7 months if anyone manages to lift it at least to 5.10 or if it happily goes EOL like i.e. Qt.
Also note how sailfish commits are already on the default branch, this clearly shows a forking mentality and little experience with keeping a repo like that moving with upstream.