Looks like these are a custom made item. I assume you are prepared to spend far north of $1000 for one of these.
I am sure the quality is excellent. Most of us plumbers, being rather pragmatic, would say " what kind of parts are in it? Where could you get parts if you need it?"
Since it is a boutique item, it apparently was not included in the Map tests, so we have no way to estimate performance. Ask the designer who is recommending this to get some specs from the manufacturer. There does not seem to be a lot of info available on their website.
Being a concealed-tank type, installation will be costly, and maintenance will be as well due to access issues.