Not quite, japantours.
If you go to your settings tab, there is a section called tracking & analytics.
Once you’re there, click on “+ New Tool” and select the “</> Custom” option at the bottom.
This allows you to make a tool with html code that will load faster than any box or lightbox so this makes it a better option than a javascript written loader through the site code and it shows on mobile just as quickly.
If you don’t know how to write your own html code, I recommend this handy tool, all you need to do is pick out a color and then copy paste the code snippet.
https://futurevisionweb.wixsite.com/futurevision/preloader
Make sure to place the code in Head.
This won’t improve load times, but it weighs next to nothing so it shouldn’t make it any slower.
Good luck!