Could be a combination of the force profile after actuation and the difference in force required. Buckling springs have a rapidly increasing force curve after the actuation point which prevents any shock from "bottoming out". Stock MX switches have a "hard" bottom out, the spring rate increase is linear throughout the movement and there is no sudden ramp-up at the end. This is the main reason why people started using orings.
If you're used to using buckling springs, the force required on MX is much less, so you could be using more force than is necessary and thus still accelerating the key when you hit the hard bottom-out point, causing shock to the fingers. I find I still do this on linear MX switches (beacause there's no physical confirmation of actuation before hitting bottom), but not on the tactile ones.
Moving to heavier MX switches may help, but ultimately you have to get used to using whichever version you choose, so you're not bottoming out strongly. I find the heavier MX switches fatiguing on long typing sessions, 62g is the ideal spring strength for me.
Try using orings / trampolines. They do help to reduce shock very well. I find 62g ErgoClears with trampolines and heavy keycaps to be the absolute best MX typing experience I have had so far.
