The way SF uses it means it’s not a superior system, it’s the same system as most other power-derived systems because it derives all the zones from an FTP test.
If I did my own power curve tests on 4 separate days (vs crammed into one test), then yes, I might have more specificity when it comes to setting my training zones. But I don’t need SF (or TR for that matter) to do that.
From my own experience, the 4DP test is nothing special, and SF is way off base. YMMV.
