I don't see the harm in adding this to be honest.
Groups that don't want to help people clear will kick when they see the new party member message pop up at the beginning of a duty anyways.

I also feel it's dishonest to join a farm group when you don't have clear exp.
I know it's hard to find groups to practice with sometimes (I have yet to clear t5+, Mog Ex, or Ramuh Ex myself) but other players aren't obligated to teach you.

If you have gotten close you can always message the party leader to see if they're willing to take you with your exp but it's their choice.
More incentives to help new players would be a welcome addition to the game though.