Also, there are many apps/teams that don't have "clients", and a spec is not really worth writing, much less maintaining. Specs are great when you are a larger

Also, there are many apps/teams that don't have "clients", and a spec is not really worth writing, much less maintaining. Specs are great when you are a larger team with stakeholders who aren't part of that team, but if you're a small tech-heavy startup moving quickly, I'd consider even the presence of a spec a symptom of mismanagement.