The number of heads I get in the shop that are being used in competition engines turning high rpm........ that have a single line of contact on the valve tip is less than 1%....... as in almost never.
Not “never”, but almost never.
It is the very rare exception.......not the rule.
That’s with 30+ years worth of examples to look at, with heads that have come from countess different sources from all over the country.

To paraphrase Chris Uratchko......... “having the valvetrain perfectly smooth and stable isn’t always the fastest way down the track”.