I haven't read this whole thread, so someone may have said this already but there is a very good excuse for him to not have kicked it into the end zone, the coaches probably told him not to.
The coaches know what the kickers can do on kickoffs as they see it in practice, not like a FG with having to do it against a live rush and with pressure. I'm sure in the preseason the coaches a lot of times ask them not to put it into the endzone so they can see how their coverage is doing. The reason it only made it to the 10 was probably because he accidentally took too much leg out of it and it came up very short.
Whoever kicks, make it happen lol