Electricity will flow regardless. The reason to pay attention to fuse directionality is to get better sound quality. And because directionality is ultimately determined by what sounds best in the complexity of not only a single circuit, but in the complex interaction between components in the system as a whole, there really is no better way to determine what sounds best than to listen. You can of course measure, but you’ll than need to listen to confirm your measurements correlate to SQ which is subjective. For these reasons it seems straightforward to simply listen and make the call on a fuse by fuse basis.
I hope this helps,
Ted Denney III
Lead Designer/CEO Synergistic Research Inc.