Me too. I add bugs to scratch and scratch does not have corn it though.I believe for people new to keeping chickens it is important to understand how and what to feed them.
Many people now being able to keep chickens in their area have never kept livestock type animals.
It is a huge learning curve.
General guidelines are helpful.
There are a lot of threads I have seen where birds are not doing well and it turns out the keeper is giving several cups of treats a day to a very small flock of less than 10 birds.
Do I stick to the 10% as a very strict rule never to be broken?
No.
On occasion I give them scratch in the morning and then some watermelon in the afternoon. Not every day or even every other day.