Many visualization experts, such as Edward Tufte and Stephen Few, consider a bar outline as you requested to be "chart junk." It adds no additional information to the chart (fact) and so, it is superfluous (opinion).
JMP favors accuracy over impact for statistical discovery, but you can request it in the JMP Wish List area of the JMP Community. In fact, there is already a wish for outlines when bars use a pattern instead of a color.