You got me on that one. I've never heard of the Summit brand/kind of Timothy Hay. I may be wrong, but I would think all Timothy hay would be about the same when it comes to feeding a chinchilla.
I have grown some hays in the house in the winter under a grow light, but with the number of chinchillas I have, it's just not practical for me.
I would think, if you have only a few chins, it would be a special treat for them and be practical for you.
A hay that is referred to as a winter hay or early spring hay seems to do better inside than one that grows best in the heat of the summer.
Keep in mind that the amount of light, moisture and temperature play a big part in growing plants successfully. I would suggest to check with your local co-op, 4-H Club, school, garden shop or someone that grows hay on their farm.
Please let us know who you contact and which ones seem to be the most helpful to you. It's always nice to know what information is available and where it is available.
Jo Ann