I’ve adjusted the rockers countless times on our racing engines for the last 50 years. I’ll set the clearance with a screw driver or Allen slightly tight and hold that position with the screw driver or Allen and tighten the lock nut. This usually loosens the clearance by a half a thousandths which is just right. I have never liked interference nuts or even stud rockers for that matter. On an off topic racing engine I purchased a T & D shaft system and can run a season of 6 to 8 races and never have them move; we turn that engine 7000 rpm at the end of every straightaway.
I find my y-block to hold its lash clearance consistently and rarely find one even a few thousandths off. I check them every oil change. I’ve watched Tim’s adjustment video and found it a good learning tool. Ted’s skill with y-blocks is also second to none.
If you having consistency problems with rocker arm lash I would be looking your oiling and the condition of the rocker bushings, shafts, and tips. Once a year I will run my engine with the rocker covers off and a cardboard shield to protect the exhaust manifolds to make sure the over flow tubes have oil flow. The left side seems to be a little quicker to flow than the right. My cardboard is wrapped with clear box tape. Good luck.