Not compatible with WP-Optimize Cache Preloading

I’m using WP External Links and the WP-Optimize plugin for server-side caching. This plugin has a “cache preloading” option, which triggers WP-Optimize to cache the site by visiting pages to preload them (so that they are ready the first time a human visitor wants them).

Whenever I visit such a site cached by “cache preloading”, all the things that WP External Links is supposed to add to an external link (CSS classes, FontAwesome symbol, rel tags…) are not there in the sites HTML source code. It’s like I had never used WP External Links in the first place. It seems like the action that WP External Links usually performs on external links before the site is delivered to the client is somehow supressed or not triggered when WP-Optimize is visiting the site for cache preloading.