Oldish, I was referring to the guy in the vid
His valve clearances are already very near bottom limits at 0.12mm, as we are all aware, on modern overhead cam engines they close up with wear, as against open up as with old pushrod motors.
If I had the bike stripped to that level and the valve clearances had closed up that much, then I would have re-shimmed to take them back nearer to top limit.
That would give me full confidence for the next 15k miles that my valves and seats would not be getting burnt.
(Dealer would not bother I'm sure)
Can't understand why he was setting lines to arrows for checking? Just check the cam clearances with the lobes pointing upwards turning as required.
Draw a plan and note the clearances for each valve, if they need re-shimming, strip out and measure shims, do the sum & fit the new shims. Check clearances again after re-assembly.
Like you said oldish, it's not rocket science, just needs a bit of care & attention to detail.
Lines & arrows will need setting up before stripping out cams on bucket & shim motors. Always refer to workshop manual for this part of the job.
Cam on shim engines can usually be done without removing cams but using a tool for the job.