Although this should probably be a moved to a new thread, the "S" is simply Canon's way of maintaining labeling continuity for its lenses that are limited to APS-C optical coverage. i.e.: EF-S lenses for APS-C SLRs and RF-S lenses for the R7 and R10 or FF R cameras used in "crop" mode. The "S" designation refers to the size of the well-resolved optical field diameter, not the lens mount diameter or the "sensor box" size.
Canon has not defined the true meaning of "S", but internet "experts" have speculated it means "Short back focus" (clearly wrong since the back focus distance of EF and RF lenses is the same as that of EF-S and RF-S lenses), OR "Small image circle" which is more accurate, but is still just a guess.
