It's more about what happens once there is an issue. I agree if something works and remains unchanged it will probably stay reliable, the issue is once you introduce a change, even nowadays you can possibly break something that isn't easy to undo (or troubleshoot without taking services down).

For low traffic stuff, might seem OK, but no redundancy for a service that users pay for seems irresponsible, however Gitea might just be for them to track internal stuff, so maybe a little less so.