I would point out that if Homer was the last surviving practitioner, and a good hundred years past when the craft was commonplace, it's a pretty easy assumption to make, that some construction details may have been lost. In the small snippet of video where we do see him applying the dry sinew, into the thick glue, he seemed to be doing a good job keeping it straight. I understand that Ishi dampened the sinew with saliva, which also wouldn't be as effective as soaking in glue, and wringing the bundle out. I'm just saying that we, as people, forget how to do things pretty quickly after the practice of them falls out of fashion. My own father grew up farming and logging with draft horses and learned carpentry with no power tools; I remember watching him build double hung windows from scratch. I barely know which end of a horse is which.