If I'm remembering correctly, when you take a cab and/or use a segment skip during a mission, the results screen won't tell you your mission time. I think it says NA or something. This means submissions with proper Any%/Any% NMS strats (for the most part) will never have a time to use for the leaderboard, even if these missions include a time stat on the results screen.

Refer to this post to see which missions do/don't have a time stat: http://www.speedrun.com/gtav/thread/1dzcx/1#1zsh0

Using the IGT would work for every Classic% submission, of course, but then we're left with a mix of IGT and RTA. I feel it's best to keep it consistent and use RTA throughout. Masks and Boiler Suits use IGT simply because they're so short.

^ We won't be doing this because, as of now, submissions that include a "without loads" time are given higher priority over over those with only a "with loads" time -- i.e., a higher RTA time will be shown as the best time on the Level Leaderboard page if it's the only submission which also has a time under "without loads".