When training volume is equated, low-repetition maximum (3RM) resistance training produces similar muscle hypertrophy but greater strength gains compared to high-repetition maximum (10RM) resistance training.

Study: Divergent Strength Gains but Similar Hypertrophy After Low-Load and High-Load Resistance Exercise Training in Trained Individuals: Many Roads Lead to Rome.

When people lift heavy weights for few reps or light weights for many reps but do the same total amount of work, they build similar amounts of muscle. But lifting heavy tends to make you stronger, especially in big movements like squats and deadlifts.

Study: Effects of Different Volume-Equated Resistance Training Loading Strategies on Muscular Adaptations in Well-Trained Men

The study looked at two workout styles with the same total work: one with few heavy lifts and one with many lighter lifts. It found both built similar muscle size, but the heavy-lift group got stronger faster, just like the claim said.

Study: Muscle hypertrophy and strength gains after resistance training with different volume matched loads: a systematic review and meta-analysis.

The study shows that lifting heavier weights fewer times (like 3 reps) makes you stronger than lifting lighter weights more times (like 10 reps) when the total work is the same, but both ways build muscle equally.