It might depend on how the Javascript is being blocked. I use uBlock Origin advanced mode to selectively block Javascript (I imagine uMatrix is similar), and always have to whitelist discourse's CDN.

The difference is probably that selective blockers like uBlock/uMatrix don't show <noscript> elements, while globaly disabling Javascript does, and discourse might be relying on the noscript element (on mobile right now, so I can't check to be sure).