I wrote the manufacturer and the responded within a few hours:
"The base paper is 100% cotton rag and internally sized with calcium carbonate for archival reasons. It might be best suited to sketching, as watercolor papers are sized (typically with gelatin) to pull moisture into the paper while leaving any pigment on the surface with minimal bleeding. The inkjet receiver surface still may have some usefulness for various art techniques …it would just have to be tested. I’ve worked with several artists that print on Edition Etching and embellish with various techniques from pen and ink, pencil and encaustic wax, acrylic paints, etc."
--Darin