It's possible that they're being slow to limit casting from scrolls precisely because all the classes/companions aren't in the game yet and multiclassing hasn't been implemented. Long term we'll have a lot more ways to cover our bases than we do now. They may view unrestricted casting from scrolls as a stopgap way to compensate for those missing options.
That make sense.
It would be so cool to ask them (and have an answer).
