I know how you missed it, the same way we ALL missed it!

Some feel it should be on Allow by default, but when you are releasing unified builds, then sometimes you have to reduce to the least common denominator, like maybe other camera models don't perform well with it set to Allow? I don't know, just surmising here.
The only buffer settings I'm aware that works best for 5DM2 is in the Canon menu set images to BLANK FOR RAW and SMALLEST JPEG files (this is camera model dependent, e.g. the 5DM3 is just the opposite - you should be able to find out which buffer settings work best for your camera in these forums). There's another one in ML under MLV module called Buffer Type (I think) and setting to 0 or 1 works well for the 5DM2.