Agree, also confused because Debian seemed to get security updates rather frequently when I've used it.
That's like their whole thing, stable and security updates. I would be curious if there are examples of exploits that weren't patched quickly on Debian stable.
The proxmox interface let's you make the containers, but you have to install the software you want to host in that container after creation.
These scripts let you run a script that makes the container and also installs what you want to host within the container and does the setup.
I used their script to set up a home assistant vm, you run the script and it downloads the HaOS install media and does the install in the VM for you, preconfigured, and starts it so all I had to do was go access the web interface.