Duanmu Huai wasn't entirely unfamiliar with being served by maids. In the Tribunal, he had maid puppets, Audrey, who wasn't a full-time maid anymore, and even maid demon beasts. However, those were professionals. They worked seamlessly—they would smile warmly, brew fine tea, serve meals, manage everything perfectly.
Of course, strictly speaking, maids were really just for brewing tea, serving water, making beds, and tidying up.
But Naruse Mio's maid scenario was a fresh experience for Duanmu Huai—after all, she wasn't a professional. On top of that, Banriya had purposely chosen a maid outfit so short it barely stopped at the thighs; any bold motion might result in exposure. This left Naruse Mio visibly uncomfortable—blushing fiercely, fidgeting endlessly, reluctant and yet compelled to perform her tasks. By conventional standards, she was clearly an unqualified maid.