Yes, this is :(, but you should be serving all your static assets through a CDN, which will have http2. I can't think of a scenario where I would want to serve anything other than the dynamic content off the heroku server. I don't think http2 buys you much there. So you should be able to get away with at most 2 requests - one to the heroku server, and one to the cdn.
The 2022 answer is actually to bake the CDN into your PaaS. Requiring a whole separate CDN for static assets is complication no one needs in their life.
The changelog that's linked in there is depressing: only updates for languages/environments and an occasional minor update to the actual platform every few months.