this is the rule as per the Little league Rule book Rule 1.08
Note 1. The on deck batter position is not permitted in LL Major Division and Below
A,R, Fenced in areas may not be used for an on deck batter
Note 2, Only the first batter of each half inning will be permitted outside the dugout between half innings in LL Major Division and below/ A.R. The next batter should be ready with a helmet on, but may not pick up a bat until it is his/her turn at bat
Note 2's A.R. does not state that the First batter of each half inning can swing a bat. wouldn't swinging a bat outside the dugot be considered "on Deck"?