I believe @Shine- 's point is that when you select DXVA for rendering it's going to be chosen all the time, so there is no fallback option. Prior to #4163 Hi10p gave black screen on DXVA rendering, but worked fine when choosing "Automatic" rendering - which essentially uses software rendering for anything not-HW-decoded, and DXVA rendering for all DXVA-decoded material. Some users have DXVA rendering forced ON because they want to take advantage of (better) HW scalers and deinterlacers e.g. for DVDs. However, I don't see the point for Hi10p to use DXVA rendering, because there's usually no need for deinterlacing or scaling. 
That said, current code has an issue either way, and I thought the proposed solution here is simple and would do the trick for Gotham, and we can address it properly after G.