brand.yml: html heading sizes do not increase with base size

I want to blow up all of my text to produce nice screenshots for slides in a demo.

So I tried

typography:
  base:
    family: Helvetica Neue
    size: 32px
  headings:
    family: American Typewriter
    color: '#11226d'

Now the main text is bigger than the headings:

brand.yml expressly disallows size on headings.

So it seems the intention must be that headings respond to base size.

We should check what the Shiny implementation of brand.yml is doing here.

In the Typst implementation, base means the base of all text: