In my experience that is not the case. Specifically because jams are waves not just slow moving traffic. A gap will open up and quickly I can be in the 3rd gear

In my experience that is not the case. Specifically because jams are waves not just slow moving traffic. A gap will open up and quickly I can be in the 3rd gear to catch up. Of course as soon as I do the flow stops again. I could just creep forward in 1st and let the rest of the flow fill in front of me... Manual transmissions are definitely hell during rush hour... but doesn't seem to affect people contributing to the waves in my experience.