Just compare the results of Ashton's current Dec PR with that of the current WR and previous WR. It's just too painfully obvious to ignore the fact that his throws are extremely lacking when compared to them.
Ashton sprints better than both of them ever did. Jumps just as far, just as high. Hurdles better than they ever did and pole vaults just as well.
Of course we all want to see him improve over all his events. But to beat that WR, and smash it to peices. He will need large improvements in his throws.