Eldritch Scion and Spell Scars - how does it work?

[Saker]

I imagine it just allows me to access 18 levels of spells without having to pull out a scroll saving me time. But I'm wondering about whether I can treat those spells as spells known for spontaneous casting?

[Firebug]

So, Spell Scars does 2 things.
1) You can cast from them as if they were scrolls
2) You can prepare your spells from them as if using Spell Mastery.

Q: As a Spontaneous caster, do you prepare spells?
A: No, you do not prepare spells. Spell Scars 2 does nothing for Eldritch Scion.

If you can find a FAQ that says adding spells to your list of spells you can prepare affects a spontaneous caster's spell known, I'd love to know.