Buckle Fracture of Wrist

My 16yr old son was knocked down in JV hoop in Feb and got a buckle fracture at the end of his radius.  The doctor put him in a molded strap cast for 4 weeks (turned out to be 5 since to doc got the flu). The doc originally said 4 weeks cast 1-2 weeks before he could start baseball.  So when he takes the cast off and xrays says everything looks good and says 3 more weeks because he squeezed the wrist and my son flinched (my son is very sensitive). [I am kicking myself for letting my wife take him]

Is this normal, 8 weeks for a buckle fracture?
Why didn't he keep the cast on, 3 weeks with his arm dangling...he didn't prescribe PT?
I gave my son a few days and he is using it as normal when I watch him, should I get a second opinion?
He had a dislocated knee cap last year and missed getting a start spot on the team because missed the first couple of weeks and he is really bummed this is happening again....

I don't want to push him but I just don't know why the doctor is taking this approach...my son seems ready (and would tell me if he couldn't) start to add some physical activity (baseball)...sure not full contact...but I just don't understand.

Thanks for any advice you have.