Squatting in ultra boosts..... Just another example of something you "shouldnt" do that really doesnt make a difference.
For the casual lifter, there are more important things than what shoes youre lifting in.
I wouldnt recommend it, but i wouldnt tell someone they shouldnt do it either.
I def think yu can keep the hips that high during a deadlift.
The starting position for a deadlift isnt the same for every person. A drop in the hips might bring the knees too far forward and throw off all the mechanics.