They're old Japanese men, so they probably don't ask the clerk to microwave the jar behind the counter - could potentially create social awkwardness. They take the jar home. Do you microwave the umeshu jar? If you ever microwave it, does it matter whether there's an actual plum in there? Or does the jar have to go in a pan of water on the stove, or something? The old men's wives or daughters or daughters-in-law probably actually handle this operation, if such are present.
Being several days into an illness and grumpy and restless about it affects me in a manner superficially similar to that of alcohol, particularly after dark.)