So whereas authors used to ship a new version, and let people upgrade to that version at a discount, the author now assumes the burden with each new release of maintaining and testing V1 (that’s with all the feature flags turned off) as well as every feature flag between V1 and Vcurrent turned on. One at a time. Sounds like insanity to me.
That would be a choice, not a requirement. It's literally a flag. You can do whatever tf you want with it. It would be trivial to have "V1 full app unlock" feature be the same as "V2 full app unlock" feature.
