As already mentioned CMYK has a lot of quirks like not having a true black or how blending modes work. If you wanted to you could do the math yourself and check what the inverted colors should be. However there is a reason why people don’t work in CMYK when creating digital images anymore except maybe right before print and for soft proofing, there are multiple topics about it on the forum, like this one (and many more).
One of the many things is that it simply doesn’t work as intuitively when working with digital images (except maybe that colors mix kinda like in real life).
Maybe someone from the dev team like @halla can shed some light on it and explain in detail why the result is like that.