I've no idea about the kids training, but each year seems to be a fast early time followed by inactivity due to injury. Would seem either being ultra cautious, which isn't the worst or alternatively his body can't deal with intensity of the work/racing.
That should ring alarm bells to anyone though, you'd hope the coach is all over that.
Bit of a waste if pushing too hard too early means you never get to explore your real potential.
However still very young so hopefully it'ill be addressed properly and he'll have a decent senior career in front of him, rather than joining the graveyard of outstanding juniors never seeing seniors.