I have maintain our Gitlab instance for the last 5 years. Zero issues, and I do a sudo apt update once a month. So I guess some people thought using the manual setup was the way to go?
The only thing I can really complain about are the constant UI changes that do not actually improve anything. I fell they are just changes for change's sake to keep some frontend devs busy.
Also, Debian/Ubuntu OS security updates happen a lot more often than once a month. I suggest just using unattended-upgrades, it can even auto-reboot at a convenient time of the day after Linux kernel security updates.