By environment sampler I meant the 'Adaptive Light solver', sorry for the confusion.
I tested this here, too, with a Corona Sun, an HDR (8Kx4K, Bitmap and CBitmap with both spherical and dome mode) and even a crescent shape with a Light Mtl, all aligned to produce the shadow in the same exact spot. Two holes in a box, one round, the other square shaped, same size... it works correctly, even the crescent shape producing (almost) same result for both holes, correctly picking up the light source shape.
I wonder if this has to do with units (mine are set to meters) but why should it matter.
Also, as this has helped others in similar weird cases, maybe reset Corona settings.
Other than that, I have no idea, a dev might have some more insight here.
I could imagine having your repro scene that produces wrong results would be good to have for others to test.