Just because a man sells guns, doesn't mean he knows everything about them all. I had to show a ten year veteran tire and lube tech where the oil filter was on my old Cadillac.
If you want the must definitive answer, contact the maker.
It is, as you seem to know, generally accepted that you can run .223 through 5.56 though, but not encouraged to do it the other way around.
Come if you must, but only if you must. For the day you find yourself upon my step, will surely be the night you find peace along Jordan's edge.
I firmly believe that any man's finest hour, the greatest fulfillement of all that he holds dear, is that moment when he has worked his heart out in a good cause, and lies exhausted on the field of battle... Victorious.
"Without the rain, we wouldn't appreciate the sun."~GGC