Disable WordPress Theme Update Checks is disable update notifications for WordPress themes. All theme check for update on WordPress.org, regardless of whether it was developed custom for a client or built by a commercial theme shop (themeforest, mojothemes, etc…) . This can be a problem if a new theme gets added to WordPress.org that has the same name as your custom or commercial theme.
AvadaTheme claims that it is the number 1 selling WordPress theme of all time. Not sure I believe that, but that amount of sales is quite impressive. Avada has been around for 5 years and always in Popular Items of WordPress theme on themeforest.