"Step" is not, as your question implies, synonymous with "channel spacing" in this context.
Rather, it has to do with how the CPU defines frequency for the synthesizer. Chips cannot deal natively with floating point numbers, only integers. So a frequency is defined as X number of "steps" (of a pre-defined offset) from a base frequency.
A totally hypothetical example for purposes of illustration:
If your frequency of interest were 460.025, then with a base of 460 and a step of .025, the frequency would be represented by the chip as the integer "1". If the base were 460 and the step were .0125, the frequency would be represented by the integer "2." And so forth.
That is why "step" has to be set on a per radio basis.
Offhand, I have no idea what "shft dev" means (assuming it means anything other than max. deviation).