That's absolutely not my experience from any of the SPAs I've worked on. If the API used by the SPA is so "specialised, single-purpose", then that isn't somethi

That's absolutely not my experience from any of the SPAs I've worked on. If the API used by the SPA is so "specialised, single-purpose", then that isn't something inherent to SPAs, only inherent to developers (or architects) who are inexperienced or bad at their job.