This seems more like a race condition, see:
$ f() { ( sleep 0.1; exit 13 ) & "$@"; wait -n; echo $?; }
$
$ f sleep 0.0
[1] 30612
[1]+ Exit 13 ( sleep 0.1; exit 13 )
13
$ f sleep 0.2
[1] 30617
[1]+ Exit 13 ( sleep 0.1; exit 13 )
127
