I think that he means to choose different forms of squats, deadlifts, benches and rows. For example choose different foot positions, different grips, incline vs flat vs decline, dumbells vs barbell, depth, etc... With all these variables there are many types of the big movements to choose from.
Squats: front squats, back squats, sumo squats, GMs (not exactly squat or deadlift but close enough), 1/2 squats, deep squats
Deadlifts: Stiffleg, Sumo, Wide Grip, medium grip, straps vs no straps
Bench: incline, flat, decline, barbell, dumbell, close grip med grip wide grip
Rows: T-bar, upright, Yates, cable, dumbell
