I think the experience varies. Was flying SUB-SIN-MAA - came in on GA, connecting to SQ. Transfer desk never questioned the weight of my back pack style carry-on- which was around 9kg. My boss was also not questioned on his fully stuffed wheeled carryon - it was max size 22 x 9 x 14. Don't even want to guess how heavy that was. We were in Economy, and had no issues.