Yes the flex does have to be on the field or they have left the game and must use a reentry to come back in.
Your example of switching pitchers and the flex goes to the bench, the flex has left the game and must reenter to come back in.
The flex is a defensive position and MUST play defense or they have left the game. I know the dp/flex rule inside and out and I can assure you what you are claiming is not correct and is against the rules.
Sent from my Pixel 2 using Tapatalk
Your example of switching pitchers and the flex goes to the bench, the flex has left the game and must reenter to come back in.
The flex is a defensive position and MUST play defense or they have left the game. I know the dp/flex rule inside and out and I can assure you what you are claiming is not correct and is against the rules.
Sent from my Pixel 2 using Tapatalk