That's right. The Ladybird Browser Initiative will only accept unrestricted donations. We're missing out on a fair bit of money this way, but we believe it's the right path for us.
I think he's saying precisely that they won't, and I support this. What is issue sponsorship but a donation with strings attached? It would mean ceding control of the direction of the project's development to the highest bidder.
I believe that's also what the Zig Project is doing. I hope that this sort of thing becomes more common, as browsers and programming languages (and many more things) really are things that we should have as "common goods" that don't have the interest of a corporation before the interest of users.