if it was a real human may be he would be able to fit his legs in the circle.
I don’t think so. There are 3 joints between the sole of the foot and the hip, hipjoint, kneejoint, ankle. If the leg is locked perfectly straight, and the pelvis does NOT move at all, which is what the drawing shows, nothing in the chain is flexible at all except the thin layer of cartiledge in each joint. Perhaps the whole leg can compress a millimeter or two, the sole of the foot is soft, and the arch of the foot is slightly springy so perhaps a few more millimeters there. But - why should it compress more when raised? When it’s pointing straight down it should already be compressed to maximum right?
You can check the mismatch yourself by opening the Vitruvian man in Photoshop, selecting the vertical leg, Transform > Rotate and place the pivot point where you think the hip might be. Then rotate (no scaling or moving). Try different placements of the pivot point.
Yeah, I guess I’ll just cheat like daVinci did.