There is something about it here, the PureOS version based on Debian 12 is to be called “Crimson”:
PureOS’s next release “Crimson” is advancing rapidly, which will be based on Debian Bookworm. After that release, we will keep putting effort in our infrastructure to be able to release new versions of PureOS more frequently so that all our customers stay up to date with the latest software and benefits that come with it.
“Bookworm” is the code name for Debian 12: Debian -- News -- Debian 12 "bookworm" released