Since version 1.1.6, we added this feature. Check the option then your page will be not able to scroll during the loading process.
This feature is for preventing your visitors from accidentally scroll to the middle of the page before the loading process is complete.
if your (or your site visitor’s) browser has a permanent scroll bar (on PC, or set to “always show scroll bars” on Mac), the scroll bar will always be visible even during the loading process.
Therefore, the page content will not move at the end of loading process – this happens if the scroll bar is hidden and then appears after the loading screen disappears, because the page content width will change at this moment.