I wonder if the manufacturers have since been able to get the non-fused disconnects listed as part of a Series Rated assembly? Or something like that.
I am most familiar with Square D products, here is some information directly from product catalog - this come from the heavy duty 600 volt non fused safety switch section of catalog.
Note table 3.12 indicates a general SCCR of 10kA, but if the switch is protected by a class J or R fuse it can be used up to 200kA.
Have to dig deeper but I also believe it doesn't matter if the protection is before or after the switch - which allows you to use them on service conductors ahead of the service disconnecting means like when you need a disconnect for a utility company meter.
Oops, table 3.12 is for fusible switches - but if using class J or R fuses you still can use with available current of 200kA, just have to look at the other table. And that makes sense to me - they use the same switch in both units, they just don't put fuse holders in the non fusible switches.