I remember reading the nutrition label of a bag of chicarrones and seeing a remark about how despite having 7g of proteins, it isn’t a significant source of protein (e.g. [0]). Reading up about it, it turned out to be for the exact reason you mentioned, namely the low bio-availability.

[0] http://www.osm-us.com/index.php?main_page=popup_image&pID=12...