Bzzt. That’s not the language used.
For programmes with falls or serious errors, SS, TR, and CO should be <9.50 and PE and IE <9.0. For a SINGLE fall or serious error, the only guidance is to not award a 10.0 in any component mark.
I am unaware of any official definition of what constitutes a “serious error,” and to my knowledge, it is not explicitly defined, nor is it indicated on protocols. Is missing a jump combination in the short programme in and of itself a serious error, or only a serious error if the reason for the lack of a combination is due to a fall? Does the fall + lack of a required element constitute two separate serious errors or is the lack of a jump combination the effect of the serious error (the fall)?
It doesn’t matter. Medvedeva had one fall or serious error in her free skate at Russian nationals. Depending on how you define “serious error,” Zagitova had far more than one (lack of combinations, multiple underrotations and falls, botched spiral). I’m not saying I agree with Medvedeva’s PCS, but hers did not violate the scoring guidelines. But he who lives by ISU’s guidance also dies by that sword. Maybe orient your pitchfork toward Zagitova’s protocol, not Med’s.
It’s nationals. The actual score values matter far less than the relative difference in scoring. There’s a reason nationals scores don’t count for SBs and PBs.