Numbers Magic Fill fails 2-week date autofill after update

I updated to the new Numbers 15. For some reason, the old Numbers autofills my dates perfectly, recognizing that it's a 2 week pattern.

The new "Magic Fill" does not, and proposes a list of repeated 2100-01-01 dates. Any idea what I'm doing wrong? The formatting is the same, as I literally opened the same file in both examples.