In Bookworm that entire section is gone, & all but the last case handled by apt & the virtual package time-daemon with appropriate Provides Replaces & Conflicts etc. in the control files to ensure only one of the first 3 OR systemd-timesyncd itself get installed. Unfortunately apt can't track stuff which people install from external sources, though perhaps the package in fasttrack should also declare appropriate Provides, Replaces, & Conflicts. Not that it'd help much when most users who use VirtualBox install from Oracle, & use the provided iso to install additions completely bypassing the package manager...