You seem to be ignoring the times when bug-fixes, and regression-fix-only patches themselves have resulted in regressions. Or when bug-fixes themselves devolve into grand-scale refactoring which greatly introduce the very real probability of regressions.
Handling regressions seems independent from where they come from. Again, if we wish to release something quick that just includes patches-as-of-this-date, then we certainly can. But the 2 are not as tied-at-the-hip as you make it to be.
