I didn't say it's a question of sales tax collections. I said a payment processor deals with sales taxes.

In this case they clearly have to exempt this transaction from sales tax in order to support it, when other transactions through their system do get sale tax applied. So the mere fact that they have to deal with sales taxes in general is likely to introduce additional complications for them even here, in cases where sales tax turns out not to be applicable.

Google don't even process the donations do they? It is a link to an external donation page.

They don’t have to exempt anything. Just let them have a link to the donate page like they always have. Which is also how nearly every donation works in the US.

It's a link to a page where you can donate. Google is not involved in the transaction. Google's rules say you can link out for donations. Google is then telling them they can't link out for donations.