[scythe]

>protein assimilability from bread is 40%

This is wrong; the digestibility of gluten is 80-90%. Your friend was probably thinking of the PDCAAS, which is more like 45 for gluten. But this is nutritional quality vs an egg white equivalent as defined by the bioavailability and concentration of essential amino acids (egg = 100 by definition; the score is based on the lowest fraction of any EAA, so gelatin — no tryptophan — has PDCAAS 0), not the fraction absorbed or utilized. For an idea of what utilization looks like see e.g.:

https://mdpi-res.com/d_attachment/nutrients/nutrients-10-001...