One rule of plumbing is...water doesn't run uphill. I don't think you'll get back flow in your second drawing (because water doesn't run uphill the other way either), you just won't drain the deeper sink (seems like a puddle will always be in the disposer) any lower than the blue line. The drain in the disposer needs to be higher than where it goes in the wall. The note you have is all wrong...the pink part won't make it work, it will only make the connections fit...there is a difference. I'd go in the wall and relo the drain connection. In case you didn't know...the only reason, afaik, for the p trap is to prevent sewer gases from entering the home, by storing a small amount of water to act as a break.

You hip to what I'm laying down here?