The "default" preset is not an actual default, but something Nvidia
decided to just call that way. It yields the worst quality per bitrate
out of all the presets, for no actual benefits. The actual FFmpeg
default is the hq one, which yields the best quality, especially when
twopass mode is enabled.
I can't think of a way to keep the "default" preset in a non-confusing
way, and as it gives no known benefits, might as well just remove it
entirely.
(Jim edit: Also made it so that if the settings have it set to
"default", it automatically treats it as "hq")
Closesjp9000/obs-studio#865
d1343dc064