Can’t optimize existing images when using the KB’s “real cron job”

Issue
The option to optimize existing images is disabled when the internal WordPress cron job is disabled in lieu of a ‘real cron job’.

As you know, the built-in wp-cron.php is extremely unreliable, and problematic. From the Knowledgebase:

[T]his file may become target of a DOS attack, or caching plugins can interfere with its execution which can cause either a lot of server load or the scheduled tasks may not execute properly and timely. This is why, you can substitute this constant file execution with a real cron job.

Current Behavior
The plugin detects define('DISABLE_WP_CRON', true), and turns off the feature.

Expected Behavior
SG Optimizer should check to see if a manual cron job is set up as described in the above tutorial:
wget -q -O - https://yourdomain.com/wp-cron.php?doing_wp_cron >/dev/null 2>&1

Alternatively, if there isn’t a way for wordpress to detect manual cron-jobs, an option should exist ( in the plugin settings or defined in wp-config.php if you’re worried about less-technically apt users) to enable Existing Image Optimization regardless.