@thovs,
the fuses are rated for the device they supply not wire size, # 10 was used for voltage drop over a long distance.
don't over rate the fuses because when they do pop at a higher amperage you could likely get burnt and broken wires especially on the smaller gauge side.
Electrician #2 is kinda correct, supposedly these S tamper resistantant parts are mostly conversions, making it possible to put modern fuses in very old housing, Edison old in fact.