What do you mean, 'most rear hubs'? All previous years Diverge models had proprietary rear hub which you can't get anywhere anymore - the reason being that Specialized missed the 142mm rear road hub trend a couple of years ago, and went with 135mm road. They're supposed to be changing that back now, but we'll have to see
most 142mm rear hubs have conversion end caps available for 135x12mm thru axle (like hope and DT swiss). Specialized isn't the only one using 135mm, but they are the only one with a 2,5mm offset cassette body, hence the conversion derailleur hanger :)
What do you mean, 'most rear hubs'? All previous years Diverge models had proprietary rear hub which you can't get anywhere anymore - the reason being that Specialized missed the 142mm rear road hub trend a couple of years ago, and went with 135mm road. They're supposed to be changing that back now, but we'll have to see