Exactly. Think of the male gaze like a camera and a director. If someone was staging and scripting each panel in the manga, what were they thinking? How is the subject of the lens being portrayed and arranged? Why is Claire devoid of a personality in these few shots, and why are they all creeper and low angle shots? You can depict this tastefully, and sexily, and with Rei's gag comedy reaction without depicting Claire like a pinup model. That's asking a lot from a not so progressive industry, but this isn't exactly a remotely new artistic concept
Dipping into markets a bit, Yuri Hime's readers are split evenly between lesbian women and straight men, so they've always had a bit of an identity crisis when it comes to the editorial department including fan service. I think it comes more from a lack of intention
Considering how universal this treatment is in manga, I don't think Villainess stands out from the crowd in this respect. Even if Claire's sudden depiction is a bit jarring.