Yes, I followed those steps specific to siteground. After I set the variable for auto_prepend_file it would appear correctly set but did nothing until I added the PHPRC line. Once I added the PHPRC line extended protection became enabled but I had multiple PHP errors appearing on my site and I couldn’t access certain Admin panel areas like plugin configuration and editing posts. A Tier 3 Siteground support person rolled my site back to PHP 5 and all the errors cleared up instantly.
In hindsight I don’t know the root cause, but after a few days of troubleshooting I’m glad it’s behind me.