Mainly, I think it would give a bit more specificity to the magnitude (not so much the nature, since the lows are sufficiently different from the highs even on standard norms) of the spikiness. So it would likely provide the same kind of information as for a more evenly-developed child for whom extended norms were relevant. Just a matter of degree. For spiky profiles in particular, it would highlight the asynchronies even more (and all the sequelae of same).

...pronounced like the long vowel and first letter of the alphabet...