They probably thought you were crowdfunding when they went onto the website and it said "Money. We always need money. Right now our funding goal is $50,000."
These fundraising platforms use Stripe Connect. It’s not a apples-to-apples comparison, because individual fundraisers are essentially their own Stripe accounts. What seems to be forbidden is fundraising under a single Stripe account for disparate purposes.
I fail to see how they might have gotten confused. They clearly allow fundraising or else they wouldn't be a partner with givebutter.