See attached movie.

On movie I show you parameters of scrolling event before disabling and after disabling of vertical scrolling in mouse options.

You can see, event not understanding russian, that scrolling event come and show me +/-40 pixels to scroll and 6 lines of text. (also scrolling works in any other application). Then I unchek checkBox "switch on vertical scrolling". After that vertcical scrolling in OS is disabled. But events in JavaFX comes and show that it is +/-40 pixels. But 0 lines. SCrollBars still show reaction on scrolling.