Edibility of giant ornamental rhubarb (Rheum palmatum)

I’m interested in the biggest and reddest rhubarbs.

With regard to large size, I came across an ornamental species on Brian’s Botanicals:

https://www.briansbotanicals.net/product/rheum-palmatum-var-tanguticum/

His page, as well as others online, report this to be a non-edible species. I’m guessing it has a higher oxalic acid content, perhaps even in the stems, but it’s difficult to find clear information as to why this isn’t considered edible by some.

While trying to look for more information, I found other sources that report that it can be eaten! Below are two:

https://www.balkep.org/rheum-palmatum.html

https://pfaf.org/user/Plant.aspx?LatinName=Rheum+palmatum

Does anyone have actual first-hand experience with this species? Have you grown it? Have you eaten it? Have you bred it?

And does anyone know if this could be hybridized with the traditional species? Perhaps such a hybrid would be more reliably safe to eat than the ornamental species but bigger than the traditional edible garden species. I wasn’t able to find information online regarding crossing of these species.

I have no idea about the edibility of large rhubarb.

I thought I would bump your question to see what others thought.