I don't think the different usage is related to an individual group rather context, particularly when referring to numbers.
E.g. 3 is a 1 digit number because that's the number of digits needed to uniquely identify 3. There are infinitely more ways to identify 3 the number with padded 0s but those aren't useful unless you're talking about combinations/sequences of groups of digits (like random numbers or PIN codes) instead of actual number values.
E.g. 3 is a 1 digit number because that's the number of digits needed to uniquely identify 3. There are infinitely more ways to identify 3 the number with padded 0s but those aren't useful unless you're talking about combinations/sequences of groups of digits (like random numbers or PIN codes) instead of actual number values.