OK, now I see the picture. Common practice here, as I was taught by the 'old timers' and to be code compliant:
Splice the neutrals 'thru' to eliminate the screwshell.
Install 'S' fuses and adaptors, sized to the AWG of the branch circuits.
That's the point.
In this case it seems like the branch circuits were
not fused to AWG but rather 20A, relying only on the new breaker protecting the existing feeder! And that's most clearly unsafe.
