Yeah, he probably did not read it, but he does bring up a good point which is that this is only an issue because there are third parties involved.
If you were sending a Bitcoin payment on your own and you by accident sent too much, there is nothing you can do about it. That money is gone for good.
At least here it is nice that there is a chance to get it back.
That is true, and there is also the point that if I copied the address incorrectly instead of the amount, it would not be recoverable. (But this is more difficult since I can copy and paste the address; I'm actually not sure why the amount can't be copied to clipboard from Checkout.js.)
Although, in this case, I was in some sense paying myself, so I would have been able to just do a reverse transaction (and eat the fees).