Yep -- agreed --- it's fine.

regarding the 1/4 inch slope it's not required for the vent --- that's more for the drain portion.
However, something I learned a very long time ago from a master plumber was having the vent branches sloped in the attic. As he described , even though it's just for air there is a certain amount of moisture from condensation and/or rain that can become trapped in horizontal runs within the attic. By having the vent branches sloped down from the stack --- or up to the stack , depending how you look at it --- allows that accumulated moisture to drain out.