For what it's worth, I own a Fluke 179, and just tested the fuses using the method described in the manual. The 400mA range shows 1.8 Ohms, while the 10A range shows 0.1 Ohms. If I connect the same probe directly from the V socket to the COM socket (not going through either fuse or current sense resistor), the meter fluctuates between 0.0 and 0.1 Ohm.

I also have spare fuses, the same Buss fuse part numbers as came with the meter. The 440mA fuse measures 0.8 Ohm, and the 11A fuse measures so close to the probe resistance that I can't distinguish it from shorting the probes together. I don't have a convenient four-wire Kelvin resistance setup, but it doesn't matter -- I'll just say that the resistance of that fuse is small compared to what the Fluke 179 can measure.

I think that posted page from manual is correct, in that 1.8 is indeed less than 12. But I can't figure out why they placed such a high upper bound on the resistance.

But as has already been pointed out, an ideal ammeter has negligible resistance. A fused ammeter must be used in a circuit such that the *other* items in the circuit will limit the current to something below the fuse rating. If it's blowing fuses, it's because you're passing too much current through it, so the fuse is doing exactly what it's designed to do, and your meter is not at fault.