Aaron A. answered 06/14/19
M.A. in Communication with 5+ Years of Teaching and Field Work
Hi there!
There are possibly some slight disadvantages for the codec because those proportions are less used and may be less optimized. However, in theory it should not matter. H.265 compression operates through blocking, and those blocks are not limited to multiples of 8 or 16, they can operate fluidly and complexly to efficiently encode data regardless of the specific resolution you chose (unless it gets too big probably).