Yes, the words are different in meaning, but not so different as you may believe. I prefer to think of 'apocryphal' and 'heretical' as semantic, near- neighbours.

Your opinion of Gelasius' document (that it does not meet the 'standard necessary for sound attribution') is fine...as opinion. But we are not of like mind on this, you and I. I suspect, strongly, that some share your view (perhaps you yourself express it for this very reason) because of where it might lead: questioning the dogma of Papal Infallibility. And what loyal Catholic would want to open that can of worms?

The fact that Pope Hormisdas, not long after Gelasius' death, declared a heretic anyone teaching the doctrine of Mary's assumption does suggest that he knew Gelasius' mind on this matter more accurately (and reliably) than anyone commenting from the murky distance of the 21st century.