Why would you hide the ability to mark an unfilled square???

I was looking for a picross/griddler/nonogram game for my phone and decided to try this one.
It starts out easily enough, but hides the ability to mark unfilled squares in the "Options" menu. Then, once I turned it on, it was a PITA to use!! I have always relied on the ability to quickly and easily mark filled/unfilled squares to complete these types of puzzles, so this style of UI made this game a no-go for me.

E. Grimm about Nonograms CrossMe, v2.2.80