The 0.35 is the actual amount helps cover minimum cost of the transaction where the % on top might not be able to recover for. So your $1 pledge, the transaction fee patreon needs to pay to the merchant provider will likely exceed $0.35 as there is the one off fee as well as some other levies that get apportioned over the top of it. The $0.35 ensures that the base amount is mostly accounted for and the % will pay for the difference as well as cover internal costs that patreon might have.I suspect it has to do with creditcard/paypal fees.
They usually charge an amount to pay through their system and maybe those fees weren't charged back to the patrons before and they now are.
I know some gameingstores in Belgium and The Netherlands charge x percentage if you pay with creditcard or paypal because of those fees.
Not sure what that $0.35 is for, but probably something like a fee to keep the patreon servers running or something.
I don't think this is an egregious move even though they are going to be making extra net revenue off of your pledge, it's just not great for $1 patrons.