This does not achieve anything, potency is controlled by genetics and nothing can chage this, a plant will only be as potent as its genetics is programmed to be.
Stressing your plant right before harvest is something I avoid at all costs.
Why anyone would purposefully damage/stress their plants after weeks/months of careful growing and right before the most important time of harvest, is beyond me!
I would suggest keeping your plants as happy and calm as possible right before harvest is the best option.
This "stem splitting" method is an old and outdated hippy theory from the 1960s when most people did not understand anything about cannabis.