Howdy Pats Poultry
Now, I could be wrong but I think the “grass being too long” issue relates more to clippings that you might be giving them.
For example, in my novice days, I had a chicken with impacted crop because I had not had a chance to mow the lawn and when I did, I popped the clippings into the run as I always did. Because the clippings were longer than usual and she was picking them up and eating them whole her crop impacted [she recovered and we still have her].
However, I believe that if they are eating grass which is still attached to the earth, they do not eat long pieces and just peck off bite size pieces.
I ensure now that any clippings I give them are from a tidy up mow only.