The hackiness continues! I'm now bundling an existing bundle again in order for it to get exported as a global variable :p There's likely a better solution, but it kind of works.
Because I have to regenerate the docs, I just tagged it as 1.4.0-beta and added typescript and postcss in there.
It turns out rollup doesn't use the same algorithm for bundling commonjs files when there are cycles as node, which breaks postcss: https://twitter.com/Rich_Harris/status/869021144191561729. Webpack works just fine with it.
This sucks to have this rollup/webpack frankenstein but I really want to be able to release and don't really want to spend yet another day or two trying to make it work well.