You probably shouldn't be cruising at 75 mph next to a lane of stopped traffic regardless. Leaving more space between you and the next car wouldn't seem to make that practice significantly safer.

I agree that the optimal behavior isn't universal though. One example I'd cite is that I always leave more space when the vehicle in front me is so big that I can't see what's in front of it since that limits my reaction time to what that one vehicle is doing rather than what's going on further ahead.