I think he believes that burning coins increases everyone else's wealth therefore even more schools could be built etc. His thesis is Bitcoin is better than property so assume he's starting from that framework
Discussion
Yeah again it increases everyone's wealth but your coins are just being diluted within millions of coins so that's not going to make a big difference at the individual level. And economic decisions are taken at the individual/group level, not all coins holders all together.
I'm not sure there's a right or wrong answer. I would have to understand which method had the most impact. But, then again, what someone chooses to do with their wealth is a personal thing. I probably wouldn't do it myself.
No matter how you do it, the net effect will be diluted like that. Some ways make it harder to tell and so are more satisfying.
But I agree with you, the net impact would be much higher when your donation to humanity doesn’t proportionally mostly goes to the most wealthy, which is what happens in the donation to humanity scenario. Effective altruism rather than stack-proportional blind handouts.