KPHX Phoenix Sky Harbor is an interesting case. 3 parallel runways, with the Southern pair being designated 7L/7R and 25L/25R while the Northern runway is designated 8 and 26. All are within 1/10th deg alignment.
KDEN Denver is different in that it has 6 runways. (12 if you count both directions!) The West runways are 16L/R and 34L/R. The East runways are 17L/R and 35L/R. Then the North runway is 8/26 while the South runway is 7/25.
The point being, I'm not convinced there's any standard or rule applied consistently for US airports. I would expect it may be part of the airport approval process for airports intending to comply with part 139 standards. As such, each case may be decided upon the basis of the study completed as part that specific airport's approval process. IOW, what's considered best for one airport may not be considered best for another airport. There are literally tens of thousands of pages of advisory circulars, regulations and orders related to the subject of airport design and approval, so good luck running down a specific standard or rule!
As such, it seems that it's not safe making any assumptions. Spending some time in cruise reviewing the airport layout and available procedures is time well spent.