Yes you are correct.
If I were you, I would not bother with the new fandangled muscular thingy.
Just purchase 8mm, 12mm and 6mm collets from the UK then all sizes are covered. You already have 1/2" (12.7mm) and 1/4" (6.35mm) collets. These do not slip. Something else that these other add on chucks will introduce is vibration and extra runout.
Hope this helps.
Les