Last week my pitcher threw the ball to first for a pick off then walked off the mound and outside of the dirt. 1st baseman was holding on the ball to see if the runner would step off. Meanwhile the pitcher walked back into the dirt behind the mound and a balk was called. He wasn't close to the rubber. We are in the pony division and are using MLB rules unless specified in the pony rule book. Was the umpire wrong by calling balk? I was under the impression the pitcher had to either straddle the mound or come in contact with it while not having the ball for a balk to be called.
I'm not familiar with Pony rules but my understanding of MLB rules is as you stated - must be touching or straddling the rubber (not "mound") for it to be a balk.
Maybe @CoachPaul will show up and set us straight.
On or astride or straddling without the ball is deceptive and a balk or illegal depending on the situation. I'm not familiar with Pony rules. Some leagues make dirt circle also a balk, but it's not MLB rule.