sort of looking at the GMK Ghidorah, the legs on that movie suit look more bird like in the way it moves from knee cap to the foot area...
and then the Bandai Heisei Ghidorah that the MA one is based on looks about similar in the leg area.
Looks like the MA Ghidorah looks more in common with the Bandai version on the leg mass.
What could maybe be throwing the eyes off is that the MA Ghidorah is being shown with slightly bent knees, whereas the usual other figures for that same suit, show the legs more straight. Maybe you can bend and straighten as you wish...maybe.