He’s not talking about donations though, he’s talking about paying full price THEN tipping. It’s a blatant excuse to pay developers less while placing financial guilt on the people paying for the product. It’s the same way tipping at a restaurant works.
To add to what you are saying, I wish they would make that message clearer. The first time I saw it, I thought they were still going to charge me for the extra copy and just not give it to me. Still not 100% sure about it.