The data can be viewed in a lot of ways on that site. I used the same site and found .04 and .05 in different ways.
It matters a factor 2. 52 gives the idea that JS isn't even linked to 1vs1 and that it might be a crosspop.
Actually if you look at the younger ages you can see that JS doesn't even train that much slower than IS for players with this length that train 1vs1 forwards. I believe that the ratio between training speeds doesn't change when players get older apart from the elastic effect. So the lower number on later ages is probably mostly due to the elastic effect which works in favor of IS for most small players but JS might often be high already.
Your info was fine, I'm just pointing out that the JS training time is probably an overestimation and quite a big one.
Crunchy! If you eat fast enough