Smut is ruining bl writing, it's an epidemic. Why would they do this to the novel...

Nothing is done to the work without author's approval.
Many times they use manhwa as a way to make improvements to the work. If she thought it was a good thing to add, then fine.

I'm not saying they're wronging the author, only that smut scenes are being inserted in places where they don't belong. It's subjective, but I can't think of this as an improvement story wise... Pretty sure they're adding smut scenes to appeal to the people who only read bl for smut.