Where the focus point is depends on the lens design.
It may get so close that it touches the glass, or even is inside the glass.
But is it? I don't know the design of this lens, so cannot tell.
But i bet you it will easily cover even larger formats than 6x6 and not have any problem with the subject being inside, instead of in front of the lens.
If you base your assumption not on knowledge of the lens's design, but on the believe that you can get too close, then know that there are many short macro lenses lenses that go to magnifications high enough to even cover LF, and still leave room between them and the subject.
It is not a fundamental impossibility.
APS format varies between 1.2 and 1.7 times smaller than 35 mm format. Sony's version is 1.5 times smaller.
So if this lens covers APS C at infinity, it will cover 35 mm format fairly rapidly when focusing closer.
I'm too lazy to do the sums to figure out at what focussing distance or image scale.
But, it will certainly do so at 1:1. Not very extreme for a macro lens. Certainly not for a short macro lens (as mentioned, short macro lenses are made short, not to provide a wide angle view, but to make getting a decent magnification easier. So we can safely assume that 1:1 is not very extreme for this lens).
So i think that the answer still stands: this short to allow decent magnifications.
The same reason, for instance, Olympus (the 'champion' of photomacrography) brought out 21 and 35 mm lenses.
Those, by the way, also work great on larger formats.