I'd be interested in seeing Aquacoat on bare timber (like a traditional grain filler) sanded flat then stained. Aquacoat says it can be done that way.

A similar process can be done with shellac as well. (The slurry method I regularly bang on about)

Good effort with the testing too. Keeping track of what's what can do your head in! (at least my head anyway!)
Thanks for reporting.