Thanks for chiming in! I remember now that you also said this on the LE community forum.

Right, that explains it. So the use would be for things other than websites or for websites that don't need to support Chrome (and also need clientAuth)?

I guess I find it hard to wrap my head around this because I don't have experience with any applications where this plus a publicly trusted certificate makes sense. But I suppose they must exist, otherwise there would've been an effort to vote it into the BRs.

If you or someone else here knows more about these use cases, then I'd like to hear about it to better understand this.