WARNING: Inrush current can damage outputs.
Care needs to be taken as blowing outputs in this way is not covered by warranty.
Any DC-DC should always be added prior to the power on the WatchMon and not after the output.
The output MOSFETs from the supervisor cannot handle a large inrush surge current when first switching on the load ( fan). We had designed it with the view of small loads. The typical inrush current is 4X times the rating far beyond the capability of the supervisor. Whilst the surge is only for micro/milliseconds, it's still too much for too long for the FETs.
By adding the fusing, you prevent these surges causing damage and it protects your WatchMon.