I'm sure most artists would agree that gigging close together on time scale and geographically is not a good idea most of the time anyway, so it's generally not a problem. None of these norms are set in stone though - festivals, artists and agents freely discuss such things, so there's really no cause for concern. It's just the way things work and should not be seen as any negative reflection on the Shepley organisers, if indeed the above request was even made to artists at the festival.

(And Cath, while you may think it looks like you are taking part in a discussion, it actually just comes across as if you are stirring, and given your own interests expressed in other threads, it might be wiser for you to steer clear of this thread if you are not going to comment on Shepley Spring Festival itself.
If you can't let the proverbial water go under the bridge......)