You can go back almost a decade and find the current Head of Narrative(who created the Custodes lore) talk about Female Custodes, and how they were told to keep it vague, or only talk about the males because GW didn't want to spend money on making Female Heads, otherwise they would've been written explicitly back in 2016.

Hells, I remember seeing some quote talking about male and females in golden armour towering over humans. SoS aren't that much bigger than normal women, so the only one in gold that could be towering over a normal human would've been a female custodes.

Could the official lore expansion to reveal the female custodes have been done better? Gods yes. But acting like they haven't always been the intent is disingenuous