What type of stain and what do you mean by stain coverage?
The advantage of Aqua Coat is its transparent as opposed to a traditional grain filler. That makes it good for Koa, Walnut, Rosewood, and other porous figured woods used on high end acoustics.
I've also use Aqua Coat as pore filler but not under a stain. The stains I did with it - not many - I mixed with aniline powder dyes and alcohol. Stain, sealer, then Aqua Coat. I've also sprayed tinted lacquer over it but never stained it directly.