Not trying to take away anything from lilliebridge he is an animal and this is his optimal way he likes to set up for his leverages but if you will notice right before the bar breaks the floor his hips rise to a slightly higher position. You dont want your hips too low or too high. If your build is not similar to his chances are your hips will be higher. I dk about your ankle flexibility but i could not see that being the limiting factor. Maybe tight hamstrings or tight hips.
Another not about falling back in the deadlift. Quite a few heavy pullers use this as a que they will rock back slightly as if they are going to fall back then explode up and bring the hips inward so they dont fall back once the bar gets past knee level ofcourse. Make sure you try some hip hinges if you arent doing so. Mkral explained that to me and my deadlift has never been better.
Im not an expert on deadlifts but i seem to be able to explain the lifts better than i can perform them. If that makes any sense.