A simple starting point, without getting into a lot of nuance or judgment is:

If the rooms or most of the rooms cannot be used for their original purpose, that's a hoard.

Ex: The beds, couches, and floor are so covered in LP records your friend sleeps in her car.

The bathroom shower is so full of single-size shampoos and soaps so you cannot take a shower or fix a leak.

The kitchen is covered to the point where you cannot cook or eat takeout without doing significant work.

The garage is full to the point where you cannot store a snow shovel or trash can in it.

The living room is full of action figures to the point you cannot sit down, or use the couch or coffee table as intended.

If it's just A TON of collectibles, organized neatly in rows, that doesn't sound like hoarding per se.

Hoarding is not just having an absurd amount of stuff-- it's acquisitiveness to the point of harmfulness, and a complete inability to get rid of things. It's distress when you have to get rid of something that is not retrievable in terms of condition.

Just collecting an immense amount of things compulsively, sure, it might be a psych thing . . . but it's not "a hoard" until you get that plain, evident, apparent dysfunction.