Stucco/plaster Direct Over Rockwool?

Hey, I just saw this comment over in the thread https://permies.com/t/82680/Whitewash-source-recipe-Canada

Mark Deichmann wrote:
I work as a mason in Canada.  Haven t tried to render/parge/whitewash straw but it would be similar to mineral wool which we often exolate with and then render/stucco.

Whoa, this guy plasters directly over the batts? How does that work? Mineral wool batts seem to be manufactured in different rigidities, but usually only semi-rigid, nothing you can't cut with a breadknife or squish a bit if you leaned on them? We're talking about direct adhesion here, no wire lath? If the plaster adheres directly, are the batts firm enough for the outer layer not to pull away from the weight? How are they attached to the wall?

I'm just having trouble envisioning a relatively soft material forming a firm base for a scratch coat, but I don't doubt this guy has some experience, so I must be missing something.

Mineral wool insulation is also available in board form. That might be able to withstand the forces applied to a stuccoed wall.

Grainger Mineral Wool Board

Yes, I think it would, but it would be FLAT. I'm trying to find something that can follow curves without being compressible, less toxic than spray foam, better R-value than straw clay, and decently moisture resistant and fireproof. Haven't found anything yet. Appreciate the suggestion though.

You can peel apart rockwool batts with your hands, so I wouldn't want to rely on it to hold the weight of stucco.
Two layers of water resistant building paper are normally put under furring strips and over the sheathing, or the studs, in places where there is no sheathing.
Stucco mesh can be cut and folded to form or follow most shapes.