AQS rules dictate you must get written permission from the designer if the quilt is not original. From their 2017 rules:
"Any quilt that cannot bedefined as an original piece requires written designpermission from the inspiration source(s)."
But they do not have any place to list if the quilt was professionally quilted by another. For that, the entrant must enter the quilt with the longarmer listed as co-entrant but that is up to the discretion of the quilt owner. Many professionally longarmed quilts are entered as a solo artist and the longarmer has no idea unless the owner tells them or they happen to attend the show.
MQX does ask about pattern and I believe they also require written permission. They also have a place to list who quilted it if the entrant is not also the quilter. Many patterns have the permission printed right on the pattern.
But what is a person to do if there is no way to contact the designer. Say you entered a quilt that Pam Bono designed. She has passed away. How do you get written permission, contact her estate? It seems to me it should be enough to credit the designer. I would think designers would want people to enter their quilts into shows.
I know quiltworx (Judy Neimeyer) asks you to send them pictures if you ribboned. But when I tried to do that with Agave Garden my email bounced. I cited the pattern and Judy as the designer but did not supply any kind of written permission. I took at as given that their website wants to see pics of ribboning quilts. MQX did not question it.
Bonnie Hunter got inundated with emails a few years ago when McCalls published the article about copyright and shows and more shows started putting in the rule about written permission. She had to blog a blanket "Permission" and begged people to stop flooding her in box with requests.
I agree with the OP that it is the right thing to do to cite your pattern or source but it has gotten overboard with having to ask permission to show the quilt. And there have been debates here ad-nausiam about it (where copyright falls in such a circumstance). I am in the camp that copyright DOES allow you to show the end product you made from a purchased pattern but certain articles beg to differ. I would think the free publicity would help them to sell patterns and they would want that. It is the smart designer that puts permission right on the pattern to avoid the debacle when trying to enter a quilt made from one in a show that demands written permission.
I think a lot of this has lead to the popularity of EQ. You can design you own quilts even with public domain blocks. The MQG is taking it to the extreme and I think it will hurt them in the long run.