I also was always wondering about these bad specifications of the 100mA, 1A ranges.
In the CLIP, these range shunts consist of R212, a 1 Ohm, T.C. 50 ppm/K, and R213, a 0.1 Ohm, T.C. 5 ppm/K resistors.
The T.C. w/o ACAL gives the apparent T.C. of these ranges, and that's about 28 ppm/K.
That's already an obvious contradiction between the specification of these resistors and the ranges.
During ACAL Ohm, that big T.C. might affect the 10:1 transfer process, which itself is obviously precise to < 10 ppm, as with the lower ranges, but it will add up into the 24h accuracy specification for 100mA and 1A.
The strange DCI specifications might also be caused by the internal thermal voltages, which can't be auto-zeroed during the measurement.. So HP included these effects generously into the T.C. spec.
If you look closely into the schematics, you'll see these strange solder joints/bridges JM 201..208. These might be used to compensate for equivalent solder junctions of the shunt resistors.
That magic stuff kept me away from replacing these shunts by better ones.
In the end, to verify the real behavior of your specific instrument, it would require a calibrated and variable current source being at least 10 times more uncertain than these two ranges, i.e. well below 10 ppm.. even the 57xxA calibrator @ 40..60ppm won't do the job, I fear.
Frank