As I suggested at the end of the post about class level = social level and HD = confidence, such an interpretation affects the way spells are gained. The common interpretation -- that levels = training -- would suggest that 1st level M-Us can't use 2nd level spells because they haven't learned enough yet. The confidence interpretation, though, suggests that 2nd level spells are trickier to cast, rather than tricky to learn. 1st level M-Us just can't achieve that level of calm and precision because they choke. Nor can they prepare more than one 1st level spell: they spend the entire day carefully perform one ritual, perhaps flubbing it a couple times, until they get it right. At 2nd level, they've gained enough confidence that they can prepare two spells in the same time. At third level, they can do the more complicated astrological calculations and lengthy incantations to prepare a 2nd level spell.
What this suggests is that there's no reason not to let PCs learn spells of a higher level than they can cast. This gives players something to look forward to -- and something to spend money on. We can even let M-Us cast high-level spells from scrolls, although they can't create a high-level scroll themselves. This is, in fact, the default for a couple versions of the rules. In the case of a scroll, all the heavy-lifting has been done by someone with plenty of confidence. All that's left is the recitation of a few activation words -- and any trained magician can do that, even at 1st level. High-level thieves can do it, too, though not as well... and I'd allow other characters who have learned "sorcery" as a "language" to use scrolls, but with a higher risk of miscast, because they lack the confidence in the use of magic that even a 1st level M-U has.