True, but it DOES recycle currency
Most reputable schools will want you to do the Upgrade while you are still current though too and/or will want you to have flown the aircraft in the preceeding 12 months. I get calls all the time for people who want to do the upgrade (or recurrent) in the A320, B737, or CRJ who haven't flown the aircraft in like 5 years, and then ask why the class can't be 3 days long...sigh...