Such a case could better define a circumference nearest to the fig­ure's upper fin­gers and the feet, but the center will move down eno­ugh to no longer be the navel.

One could argue that the original circumference was conceived to es­pe­cial­ly encompass the legs apart; but if the same, as a tangent, would cut the feet, how could it contain them without pain, given that the legs have the same length? There are several things that Leonardo did not view.
Maybe this model was representative of an imaginary symbol, not of a sci­en­tif­ic tool as it evades all the rules; but even so the design does not suit the original re­quire­ments, though born and famous as Vitruvian.
Inter alia, where the feet of a standing man are regular, it makes little sen­se to pla­ce them as if the man were standing inside a circle.

That's what happens when one strives to embed the spiritual sphere into the material dimension. Perhaps, the spiritual component – which is not a synonym of 'emo­tion­al' or artistic – was not so much advanced in Leonardo Da Vinci as it was his imaginative and implemental intelligence.

Whatever mysterious super-esoteric coding you want to at­trib­ute to this draw­ing, Le­on­ar­do has historically reproduced – at all his way though – an ar­chi­tec­tur­al pro­file of the human body, out­lined cen­tu­ries ago by the great ar­chi­tect Vitruvius Pollio, framing it without re­spect­ing the can­ons, in an arbitrary and anatomically mistaken geo­met­ric structure.
And this is the only certain thing, among the many speculations.

Men love all the more to weave mysteries around their lack of un­der­stand­ing, the less they know about and the more this makes them un­ex­plored, fueling the renown of those who investigate, but not with­out am­pli­fy­ing the volume of falsehood and deception.

Withal a beautiful, evocative logo, it survives over time like other mas­ter­pieces, and indeed it gains the greatest fame worldwide.
Except that the circular apparatus, the one that should really make spe­cial "the proportional relationship of the parts", as is, it comes out lit­tle more than a luxury comic; if not a caricature. Wrong?
Should we need a help from The Simpsons to oversize such im­bal­ance? isn't it another silent complaint?

Uh, I disregared the fact that “part of the genius of Leonardo's depiction is that the superimposed body allows for views of 16 combinations of the­se out­stretched limbs”.  Wow!
That if we consider to combine one­/two legs normal and/or shorter with one/two arms normal and/or lon­ger, the sketch will turn indeed to a fan­tas­ti­cal ka­lei­do­scope!