Rocker shaft maintenance

Browsing thru my manuals I noticed a procedure for refitting rocker shafts which appears needs to be done before you adjust your valves

the rocker shaft is a cylindrical piece with 2 grooves on each side that need to be lined up 1.5 mm in the bores, so while viewing the rockers you do not see them as I recall on my last valve adjustment I could see some of the grooves on my shafts
On each side of the rocker shafts their are 2 cones that spread as you tighten the 5mm allen screw to 13ft lbs,the spreading tightens the rockers in the case and prevents turning or axial movement also it states thattightening them ensures the interior of the camshaft housing cannot leak oil to the exterior

So it appears to me unless you reposition and center each rocker arm on the rocker shaft each valve adjustment you will not get
an accurate valve adjustment

Has anyone done this procedure and noted how it can effect the accuracy of your valve adjustment?

Once thr rocker shafts are centered in their rocker arms they do not need to be recentered, unless they come loose and move out of position. If properly tightened that won't happen.
Bob W.