HODLing it in custodial exchange or own wallet wouldn't change the fact that they hold their investment through time and didn't sell it.
So I would consider them as HODLER's the definition of a word doesn't change no matter what they use to keep their investmenr.
The risks are bigger for such hodlers, because they don't have full control over their coins.
That's why we can't say that they hodl appropriately, although they still do it.