When you have done it (or not) as recommended...you'll understand why the Pro's on this forum answered as they did
I rotated my engine a lot when timing, rechecked everything several times... I want to do it again... The valve train has play that affect the timing, not the valve lash only. The real result will be with the final and by the cam manufacturer recommended valve lash.
Note! Cam specification is often at 0.04-0.05" lift and 0 lash.
my notes when timing: 0 lash need more than no lash between valve and rocker arm, there is a play rocker arm and it's axis too....
True TDC is another thing to find exact 0 for the degree wheel. I did it the complicated way not using a piston stop...
I'll make one for next timing session, bolt thru an old spark plug.
It's easy to implement errors, 1-2 degree here, another degree there. Total 3-5 degrees wrong. My engine runs fine now, but I THINK the cam need to be advanced 3-5 degrees.