Sounding Heretical, Sounding Frum

I was reading Menachem Kellner's Science in the Bet Midrash: Studies in Maimonides, and at one point, on p. 295, he mentions "Maimonides' notorious claim to the effect that the Torah as we have it is a concession to the primitive character of the Israelites leaving Egypt." On this sentence, he has the following footnote:

To traditional Jewish ears this sounds shocking. Indeed, Maimonides himself wrote about it: "I know that on thinking about this at first your soul will necessarily have a feeling of repugnance toward this notion and will feel aggrieved because of it" (Guide, III.32, p. 527). But the fact of the matter is that in structural terms, Maimonides is making a claim very similar to that made by Kabbalists; only when they make it, it sounds very religious. When Maimonides makes it, it sounds shocking. There is an important strand in Kabbalah, expressed openly by Nahmanides, amongst others, that the Torah as we have it exists in its corporeal form only because of the sin of Adam and Eve, and will cease to exist in the form in which we know it in the messianic era. I have a hard time understanding how that differs in structure from Maimonides' position (I realize that the music is very different.)

So, why does one sound very religious and one sound shocking? I have my own thoughts on the matter, but before I prejudice anyone's thinking, I would be interested to see suggestions in the comments.