Can't easily comment without reading the book because you have paraphrased. Is the wording directly contradictory? What are the scientific references used by LCLF?
Studies on penetration of hydrolysed wheat
The use of radiolabelling techniques to mea... [Int J Cosmet Sci. 1997] - PubMed - NCBI
The Natural Haven blog refers to textbooks and published studies so, as a fellow scientist and in the absence of any contradictory research, I'll plump for that. It also fits in with what is known about fatty acids penetrating or not based on size. 'Curl chemist' Tonya McKay's take on it
Proteins: Why You Should Care
Another science based opinion, which brings both 'sides' together somewhat
Revisiting the Idea of Protein Overload | Curly Nikki | Natural Hair Styles and Natural Hair Care
More from Natural Haven
THE NATURAL HAVEN: Moisture Issue: Proteins and moisture levels!
I haven't seen the Gliss mousse but will look out for it, thanks!
2a-2c, medium texture, porous/ colour treated. Three years CG, growing out mechanical and chemical damage = breakage and very high porosity. Past armpit length heading for waist.
Treatments: Komaza protein, Komaza Matani, coconut oil with sugar syrup. Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss ultimate volume
Styler: Umberto Giannini jelly, Boots curl creme, Rockin RInglets
Experimenting with: Mega-Tek, Curl Harmony reviver, Elvive Full Restore 5.