Looks like 95% plywood. Not much thickness for sanding & refinishing.
Helped with a 39' custom a few years back. Floorboards were a vacuum bag laminate of corecell, epoxy glass both sides, and 3/16" of teak with ash bagged to that. Floorboards were limited to a 24" width to fit into the drum sander at the local millwork shop. No problem at all to have the shop take off 1/64" and then spray on a new coat of varnish.