I can cast a basic spell + chaos symb without issues. Never worse backlash than the "splitting headache" and I've been at it for months.

Casting an intermediate spell without a symb is incredibly unsafe to the point of being unusable -- and it doesn't even teach as well as the basic+symb.

Both spells are non-tm/debil/cyclic, and are the same mana type.

This just doesn't make sense to me. I've confirmed with discern that they are indeed the difficulties I think they are. It doesn't seem like it's the spell itself, as I've tried with a few different intermediate spells of the same mana type and the intermediate is always the more dangerous. We had a red name confirm recently that most spells are on a template anyway and "more dangerous spells" aren't really a thing anymore anyway.

What am I missing here? How is it more dangerous AND easier to cast?