I hear what you're saying but I feel differently. I've done Okinawan Shudokan as well as Judo/Jiu Jitsu/Kenpo/taekwondo with my fav being Shudokan being the purest and most spiritual of them all. I feel lower ranking to fight against much more experienced instill a sense of impending doom unless your confident level is so high, it can exceed fear. Now granted you need that fearlessness to be successful but I feel until you have grasped sensible baseline fundamentals and grow in confidence. I think it will work against them in learning. They would tend to spar more reserved and timid actions. Whenever I was challenged by lower rank. I was the one who got hurt the most because they tend not to have any control :)

By the way, if you're sparring in a compassionate env is one thing but when your senior jams and/or breaks your fingers/toes and continuous unrelenting. Yeah, a little fear tends to creep in when you're sparring higher rank.