You should always consider a webnovel as a rough draft the moment it receives an official publication (which is usually a light novel, but sometimes it's a manga adaptation and skips a light novel publication entirely), as said publication becomes the official canon and source material for further adaptions. In the process of creating that first publication (like rewriting the entire thing into a proper novel in the case of light novels or working with an artist) some things can change. This can be due to the presence of an editor, publisher regulations or sometimes the author wants to change stuff themself for whatever reasons. It's pretty normal and par for the course that any official adaptation is different from the (unofficial) webnovel.