Hello -- It's true that a "slow blow" fuse is not likely to blow from
a short duration spike.  However, one important reason for the smallest
possible fuse is to offer protection from a shorted MOV.  MOVs can
absorb transients without damage or they may blow to bits or they may
fuse into a dead short.

Last winter a major electric power surge (most likely caused by snow
unloading from a 12 kV line, sending it on to the 60 kV above) put
out the power and destroyed most of the sensitive devices connected.
Most equipment connected to an industrial-size UPS survived, although
the UPS didn't.

What scared me the most is that when the power was restored, a surge
protector and power strip on my desk burst into flames and started the
desk on fire.  In this connector strip, the circuit breaker was wired
after the MOV.  If I had not been home at the time, I may not have had
one to return to.  Had there been a fuse before the MOV it might have
blown when the power was restored, maybe even a slow blow type.

The whole house surge protectors that I have installed in the circuit
breaker panel are required to be connected to dedicated circuit
breakers at their inputs.  These circuit breakers have blown when
subjected to surges but breakers without MOVs ahead of them did not
trip.  So the MOVs must be well matched to the circuit breakers.

Best regards,
Spencer Chase
Northern California