To be clear, I think the technicality the author is alluding to is that it is not all runs, because some runs of zeroes are significant, you can't condense the

To be clear, I think the technicality the author is alluding to is that it is not all runs, because some runs of zeroes are significant, you can't condense the zeroes in "ff00:..." for example, for obvious ambiguity reasons. I believe using "some" was just a way to allow for that while not describing the rules in detail.