Yes, they do, at least the JS secondary of 1v1f.
I actually attribute these different training-increase versus height as conscious design decisions.
1v1 forwards is good for getting some IS on short guys, but not as much for tall guys. Those tall guys are thought to get better IS training via IS@C. THis is similar to the fact that IS secondary of JS forwards has a declining IS training v. height.
In contrast, short guys and guards can more easily get JS from some combination of outside shooting, jump shot guards/wingmen, and 1v1 guards.