One social media user said Warhammer has 'retcon the lore', meaning including a piece ... fantasy fiction introduces a character called Custodian Calladyce Taurovalia Kesh using female pronouns.

it is just confirmation of new lore introduced in the new 10th Edition Adeptus Custodes Codex, which includes a story about a Custodian Calladayce called Taurovalia Kesh who goes by she/her.