Track erratum 1913
Erratum 1913 corrects the sentence that says a numeric BYDAY with
FREQ=YEARLY is an offset within the year "when the BYWEEKNO or BYMONTH
rule parts are present", which contradicts the clause before it, to say
"are not present".
The behaviour it asks for is already there, because verified erratum 3779
corrects the same sentence to the same effect and is already on the list.
This is a gap in the checklist rather than in the code.
Found while checking whether discarding the numeric part of a BYDAY when
BYWEEKNO is given was right: under both the published sentence and either
correction, the number cannot mean anything once BYWEEKNO has fixed the
week.