"Also, the ending *-u is still preserved, although functionally reinterpreted, in the forms of some singular patterns as well: when the original stem ended in a vowel, for example *u in *ḥāruw '(the god) Horus,' *-a in *ḫupraw 'form,' or *-i in *masḏiw 'enemy,' the ending was maintained as a glide, often written in good orthography as <-w> in the case of *-aw as opposed to <-ø> in the case of *-iw or *-uw: <ḫprw> =: *ḫupraw 'form,' <ḥfȝw> =: *ḥaf3aw 'snake.'"Stated more directly, he's claiming that the *w in *ḫupraw was written by scribes according to "good orthography" while strangely ignored in *masḏiw and *ḥāruw despite being present in all these words. It's hard to understand why that would be so. It's rather as if we have *ḫupraw with *w but *masḏi and *ḥāru without. But then this would be inconsistent with what he's stated on the development of the case system from Pre-Egyptian into Old Egyptian.
So it seems that either I'm missing something here or his theory needs a few tweaks. If I ventured an attempt at revisal, perhaps we could try Pre-Egyptian nominatives *ḫaprúwu, *másḏiyu and *ḥārawu. After reduction of unstressed vowels, this becomes *ḫaprūwa /xəpʰˈɾəwə/, *masḏi /'masɟi/ and *ḥāru /'ħaːɾu/ before the case ending was omitted altogether: *ḫaprū, *masḏi and *ḥāru. I contend that only the first word ever motivated writing w. I question its existence altogether in the pronunciation of the second. In the third, 'hawk', I suspect the word was built on the notion of 'that which is above', consisting of *ḥar 'above, upon' and an ancient masculine suffix *-aw, becoming therefore *-u. As such, it couldn't have consonantal w during literate times either since we have only a short vowel. This then explains Loprieno's "good orthography" which now reflects a transparent, underlying reality. No more arcane scribal rules on whether or not to write the trailing semivowel. No more wildcard symbols either, as I've shook my fist at beforehand.