I completely understand....and I am move envious than anything as I am not willing to take the risk with my 4 year old DD, so I am just trying to level the playing field.
I wouldn't have been willing to do SR with a 4 year old, either. Of course, it's 7 and up so that's moot. No one gets to take such a risk with a 4 year old.
When my son was 4 he was an annual pass holder. By the time he was 7 we had been to
Disneyland many many times. He knows the deal at Disneyland. He's also been to Universal Orlando, where they allow you to ride alone at 48" (assuming you also meet the height requirement for the given ride), which I figured out AFTER he had us go on Flight of the Hippogriff 14 times in a row. At the end of the day when he went on a littler coaster 15 times in a row, he went ALONE. I sat on a bench, LOL.
So he's a pro at rides and a pro at riding some rides alone. He takes aikido and therefore knows how to YELL if he's feeling weird about something. We know that Disneyland Resort has cameras everywhere and CMs are everywhere. Have you ever ridden Grizzly, and heard a CM over the PA system telling people to sit down? There are CMs up in the "mountains" that you might not even notice, watching you on the ride, making sure people don't stand up, etc.
Like others I don't know what you mean by leveling the playing field, but still, it's moot for you since your child is too young.
If that was exactly how it worked it would be great, but I have personally seen that is not always the case. I have watched people in the SR line ride together, I have also witnessed them riding by themselves in a car. If the SR line was truly used by Single Riders than your premise would be correct, but since so many "groups" are going into the SR line I feel it does slow everything down, as the CM's are doing their best to keep both lines flowing.
And that is the choice of the CMs at that moment in time. It's not ever the way it is supposed to work. I've seen CMs trying like crazy to get a party of 1 or even 2 on rides like TSMM, but no one listens! It's a huge bummer they got rid of the SR line there, because they send so many vehicles out not full.
CMs can make decisions like sending a "chunk" of people from the SR line through all at once to lower the SR line, or for whatever reasons they have.
Just remember that if you're watching from outside a SR line you have NO idea if people are together or not. At least not 100%. On my solo trips I take the time to chat with those around me, especially in the SR line, and to a casual observer it might appear that I'm with a group, when the reality is I just met them. The RSR SR line is especially conducive to this, since it's longer than many SR lines. The first time DS and I went on RSR, we had extra time in the SR line because of a ride stop that we gambled on by waiting out, so by the time we got to the seating CM we were buddies. DS didn't ride with me, but he rode with one or two of the people we had waited with, which was neat.
And when we all saw each other at the ride photo screens, we greeted each other like long-lost friends. Even though we had never met before and we never saw them again. Just never know!
Thanks for the backup sonnyjane!