The heelstrike is interesting because this is how humans typically walk when wearing shoes. Mid-tarsal break theory allows for heelstrike and toestrike walking. Apes who have mid-tarsal break walk with both gait patterns (see 6 min mark of this video).
The extension of the toes is suggestive that this is something other than a man in a suit. It is conceivable that the man in the suit is wearing big floppy feet and centrifugal force is causing them to bend up just before heelstrike. There are two main problems with the floppy foot theory, the gait looks too natural/fluid to be wearing floppy feet, and the feet don't flop around at any other point in the film.