I see what you mean. For any compound lift, squat bench or deadlift, you want to have the weight distributed across your body as evenly as possible. When you conventional deadlift you cannot "squat" it up because it needs to be one fluid motion between your legs and back and hip motion. If you use all leg force first, you'll have extended legs, but your back will struggle VERY hard to lock out. If anything, "squatting" a deadlift would be easier with sumo... check out ssjbobb on instagram. He does USAPL and his deadlift stance is very hybrid sumo, with a very close sumo stance to activate as much leg drive as possible.