If this is the case why do you include information that comes with your fuse telling you the current should flow left to right as you view the fuse from the S to R? If it’s just a lottery.
I have 4 fuses in each of my pre and power amps. It’s pretty ridiculous to expect someone to try each fuse in both directions each time you fit a single fuse in terms of time consumption (fitting and testing) whilst trying to mitigate expectation basis. Particularly as the difference between a fuse one way and the other is not night and day but relatively subtle in my experience with all audio fuses I've used (AMR, SR, Black, Blue and Orange)