Paperless Drywall as Hearth Board

I got curious the other day and started looking at the specs for paperless drywall. It's drywall with the combustible paper facing removed and replaced with fiberglass web. It's classified as noncombustible, and some types are used in firewall-type applications. It's starting to appear at the big-box home improvement stores.

Drywall has an R-value of .45 per 1/2", so it's about two times better than Durock. It's not particularly hard, but I suppose it might work bare, or covered with metal or some such, or tile.

Would this make valid hearth protection? My stove manual simply says "noncombustible with an R-value of .446 or better". It doesn't seem to require fireproofness (drywall breaks down under fire conditions, absorbing heat and giving that 1-hour fire rating).

Same thing - fiberglass. The paper is removed to prevent mold.

From what I've read, the only reason that ordinary drywall is considered combustible is the paper facing -- without it, it can be placed near combustion appliances, etc.

I just dug up a paper on breakdown of drywall under heat. The majority of breakdown occurs between 100C and 200C. Would that ever occur in normal stove operation?

The old tile-on-drywall technique is a classic of contractor cost-cutting. Our upstairs shower is made of it . True, it might not make the best floor, but a hard covering helps. There are a number of gypsum floor leveling products.