Not all pitchers or those with cannons (throwers) are great runners, and certainly not all runners are great throwers. By the end of HS my son was working with a track coach to improve lower body explosiveness and his running/sprinting form – he still does.
The other day he texted me a link to this video, with the caption “Throwers – lol!”. It’s funny because the big guy is Brian Oldfield (1945-2017) the first person on history to throw a 16lb shot 75’ – and I’d spent some time with him my incoming junior HS summer (1980). Here's the only photo of me putting a shot (also 1980 - my nickname was Lurch - wonder why? gotta love those school supplied orange shorts) - I was 16 years old and my PB was 52' with 12LB (not special) - I was better with the disc - 171'.
Thursday nights all comers meets at Los Gatos HS during the summer of 1980, the best track athletes in the US would often show up to compete, hangout and mix with the local HS athletes. I once threw the shot between Brian Oldfield and Al Feuerbach - two Olympians... Great memories, I didn't make through HS in 81, I needed to support myself - at least I looked like an adult...
If you look at the linked video, you can see what an amazing (explosive) athlete Oldfield was but wouldn't say he ran pretty. If your son has a plus arm, is he also a great runner? My son is not (I was not), what about the rest of you with plus armed kids?