I'm finding it difficult to find a straightforward explanation of what U23 means, so for the sake of argument I'll assume that anyone born on 1/1/2002 or later would have qualified as U23 in 2025.
I think you're a year out. I think you have to be
Under 23 for the entirety of the calendar year. So you'd have to be born on 1/1/
2003 or later to guarantee that you are still 22 on 31 Dec. I'm sure I've read that somewhere but I don't know where.
If we look at the Tour de France Femmes, it's quite clear what the rules are:
The tour de France Femmes rules say
https://storage-aso.lequipe.fr/ASO/cycling_trf/tdffaz25-reglement-en.pdf
ARTICLE 9. BEST YOUNG RIDER CLASSIFICATION
The best young rider classification will be contested only by riders born on or after 1 January 2003.
A case in point is Ella Wyllie. She was born 1 Sept 2002 so was actually still 22 at the time of the race, but alas, considered too long in the tooth for the white jersey. Shame because she came in 12th, 7 places ahead of the White Jersey winner Nienke Vinke.
I think what you have above is Under-24. The current TdF white jersey is Under-26. Of the ones on your list only Gregoire, Blackmore, Martinez, Romeo & Fredheim qualify as U-23 (I think. Usual caveats...). That would be a pretty limited field, so maybe U24 might be better.
I'm not 100% certain of all this. Although I'm certain of what the TdFF rules were this year, I'm not sure if they align with what U23 normally means. The more I look into it the confuseder I get.