One man army apps are generally dead simple to maintain and bug-fix. You write all the code, so when someone pings you with a problem you know exactly what caused it without any need to check for anything. I’ve maintained apps like that for years and have sometimes pushed a code change directly on the GitHub app on the phone and just checking if the site is fixed after.

Another point is if you’re also your own product manager and you designed every feature yourself, I think there’s a tendency to think about all the eventualities for each feature more thoroughly, so your code and product is kind of complete - thus you actually get fewer bugs. In my experience most issues in software come because the engineer misunderstood the requirements that someone else wrote anyway.