Not correct; 10th edition core rules came out last summer, but the custodes codex this comes from was officially released on the 20th April 2024, it literally all happened just a few days ago. (Regarding the date discrepancy, people had preview copies before the official release, but that is also why the first most people knew of it was a tweet that came out before the codex release)
Not quite correct, there were female models in power armour released with “rogue trader”, but very little lore and nothing specifically referenced female space marines. When they began actually writing 40K and 40K lore then they introduced the concept of the geneseed and it only working on males and they also introduced the sisters of battle who are indeed females in power armour but are not considered to be “female space marines” as such. None of it was actually retconned, it just wasn’t explicit in “rogue trader” and later became so when the first actual 40K edition was released.
The 10th edition Custodes codex this comes from was released 20th April 2024, AFTER the tweet. 10th edition core rulebook came out last year but doesn’t mention female custodes. So if the article says this is from a year ago it’s wrong.
Why Warhammer 40K fans are freaking out over a female Custodes in the new codex (www.polygon.com)