Clarification for Grim Hollow's Apocalypse subclass level 6 feature Arcane Apocrypha

Designing a multiclassed character with 1 level in Paladin and 7 levels in Sorcerer. Just wondering what the limits on Arcane Apocrypha are. 

"... Whenever you finish a Long Rest, you can create one Spell Scroll at no cost. It must be a spell of level 5 or lower that you can cast. This Spell Scroll disintegrates when you finish a Long Rest."

Are the spells that available for this feature only the spells that you have prepared? Or is it open to any spell on your class spell list(s) (so long as it is a spell level of 5 or lower)? My argument would be that the feature is open to any spell on your class spell lists. I am thinking of the mechanics of Spell Scrolls set a precedent for it.

"...If the spell is on your spell list, you can read the scroll and cast its spell without Material components. Otherwise, the scroll is unintelligible..."

You don't need to have a spell prepared when using a Spell Scroll, it just needs to be on your spell list. For more context, I am thinking of putting an upcasted level 4 Find Steed from the the Paladin's spell list, that I would not have prepared or normally have access to, onto the Spell Scroll generated by Arcane Apocrypha. 

I'm not playing this character any time soon, so I don't have a DM/GM to rule on this, so I put this hypothetical up to the masses. Appreciate any input.

My instinct would be that "a spell you can cast" means...a spell you can cast. If a spell is on your class list but you don't have it prepared, you can't cast it, so it's not "a spell you can cast".

Consider also that the general rules for crafting spell scrolls explicitly require that you have the spell prepared the whole time you're working on creating the scroll.