Changes to core plug-in files?

I have attempted to update portions of my site (www.andpi.org) using WPBakery’s Visual Composer. I was unsuccessful in formatting text and contacted WPBakery and was told that I needed to deactivate and remove the Visual Composer and purchase and install their new product “WPBakery Page Builder”. But as you can see from their note below, they also recommend that I contact the theme author (MINTI) to see if core plugin files have been changed before I proceed. Can you answer that question?

“The issue is because you are using an older version of visual composer (now WPBakery Page Builder) which is 5.1.1 and should update it to the latest version which is 5.4.5. You need to deactivate and delete the older version of the plugin from theme and then install the standalone version which is purchased by you. However, we would also suggest you to re-confirm the same with the theme author before proceeding, because if he has done any changes to the core plugin files, then they will be lost during this process, which in-turn can affect the content/layout at your end.”

Ticket