ceramics clay as fireclay

We just made a quick Friday run to make sure we had the materials to start our walker cooktop masonry stove this weekend. Problem was the place we got the firebricks didn't have any fire clay and wouldn't for weeks so we raced to the ceramics supply store before they closed to look for some light color clay that might have the same properties. We wound up with stoneware clay which has a little grog in it.

product shown here

is there any reason this wouldn't work?

Hi Dietrick,    Building one of Matt's cookstoves is on my list of things to do one of these days. I look forward to seeing your build progress.

I looked at the link you gave for that stoneware clay. Other than being more expensive and probably overkill for what its doing, I think it'll be the best mortar on the block.
Just be sure the grog is not too big as your mortar joints will be limited by the thickness of them, otherwise you'll have to screen them out.