“But it does NOT SAY that Governor Reeves actually made an Executive Order REQUIRING customers to wear masks.”
OK, them what’s your problem? Don’t wear the mask. From what I gather, Mississippi health department is strongly recommending you wear a mask, but not mandating, so why are you asking that question in the first place?
If a particular store is telling you you have to wear a mask to shop there, you can either do that or shop someplace else or sue them.