Honestly Soritas armor is a perfect lore bit. The Ecclesiarchy isn’t allowed men-at-arms after a wee bit of massive civil war, but just so conveniently had a leftover all-female warrior cult that had just proven its unwavering devotion to the Imperial Cult, so everyone just shrugged and let the galaxy’s most obvious loophole take effect just so long as they make it very clear that they’re not men-at-arms.

That’s the kind of disfunctional bureaucracy that the Imperium needs to bleed at all times.