
You do have a bit of a point rhere. But i think it would look weird because of the position of the human ears. Animal heads are shaped differently, proportion and all, so their ears always stand very high on the head and usually above the eyes. Also the elongation and fur would sort of work on the FL because she is a fox as it can be sort of stylised due to the size of them. The ML is a panther so his animal ears are significantly smaller and it would look weird to have the small ears replace his human ones so low on his head.
At the end of the day the pretty art is a big selling point of a lot of manhwas so making the character look unappealing during their manifestation in a josei comic is more likely to bring down sales.
Although the author could have done double change, have the human ears disappear into the head and be moved with fur for smoother transition between the hairline and the neck skin and at the same time get the animal ears on top. I've seen characters with animal traits drawn like that and I thought it looked very pretty and made sence anatomically
Another animal eared mc with a second pair of human ears... I've seen this multiple times on novel covers smh