Backpack policy: intentionally vague? Is a 12*12 backpack ok?

Coming for Sunday, and want something to carry rain gear etc. Language is vague in multiple places. Some say "Large bags and backpacks are not allowed" (so like, just large backpacks? Or all) Other places it says backpacks not allowed period. But then they have a dedicated faq section for "Are backpacks allowed?" And instead of saying yes or no it just says that only bags 12\*12 are allowed in the festival.

Sooooo if I have a backpack, but it is under 12\*12, is that fine?