Of course snapshots aren’t backups. It is a wayback system to restore whole system, like when upgrading Ubuntu or do something else where ordinary backups aren’t enough.
The scale and purpose is totally different.
If your forum is in Ubuntu 22.04 and you want to use upgrader of shell to get 24.04, then a snapshot is what to use. Sure, spinning up a virgin VPS, installing brand new Discourse and then restoring backup is another way. Not so funny way, if one has installed something else too and customized system.
If you upgrade Discourse itself, of course you do backup — do you remember close that fprum then too 
But if your database is messed up badly at that procedure, a snatpshot would save your skin easily.
So, it isn’t question of right or wrong. Those two are different tools.