LMSC
So, theres an “ If ”!!
If the lever slips out of the hand and the new flush lever is in use (pump on during lowering the lever) AND therefore the system is full of water AND you let it slip when near the bottom of travel, then the safety side will work .
If works simply be creating a damping effect due to the single hole but needs the water to create the damping.
I personally dont want the insurance the safety system provides.
But, I do prefer the blind sleeve and it’s shower screen therefore i have 4 x holes (1mm diameter) which i prefer as theres no restriction on fill rate and no drilling but therefore also no “safety” aspect. Still would be slower than the original open sleeve but wouldn’t want it hitting my jaw!!