If she was one in 2020, she should be 5 in 2024.
1 in 2020
2 in 2021
3 in 2022
4 in 2023
5 in 2024
(Yes, I counted it out like that-- my brain didn't want to do math either.)
When "everyone knows" something, they often do not bother to document it. Or maybe some have documented it, but I haven't tried the right search terms to find it :idunno
I know they change over the first few months, as they grow. I've seen it myself, and I've seen photos showing that much change.
https://www.backyardchickens.com/threads/5-week-old-mille-fleur-duccles-roos-or-pullets.818299/
This thread has photos of Mille Fleur d'Uccle chicks at 5 weeks old...