To optimize the kettlebell swing and effectively target the glutes and hamstrings (posterior chain), the movement must be performed via a hip hinge rather than by excessively bending the legs (squat style).

noli's read

Squat University is relaying a fundamental principle of physical conditioning here: the classic kettlebell swing is primarily a hip hinge, not a squat. In terms of effort distribution, this distinction is solidly validated by scientific research. An electromyography study by Del Monte et al. (2020, observational) proved that the 'hip hinge' style generates significantly higher hamstring activation than the squat version. Furthermore, the biomechanical analysis by McGill and his team (2012, observational) confirms that this hip hinge massively recruits the glutes to propel the weight. While the squat variation logically shifts the workload toward the front of the thighs (quadriceps), it causes the swing to lose its primary function of strengthening the posterior chain. Only the claim of being able to 'perfect' this complex technical movement in a few minutes is slightly optimistic, as integrating a new motor pattern requires consistency to become automatic.

the sources

No named source held this one up — that absence is part of the verdict.