Hello @jms,
We have rechecked the issue.
Actually we have multiple plugins using __
prefixes.
Only WPDM plugin alone is using 1200++ lines of codes with __
prefixes.
Already different users of Pantheon are coming to our forum with different related serious issues.
But it is impossible for us to update all the prefixes because of the issue of Pantheon.
I would suggest you to take necessary steps to make an exception for wpdm and all the addons of wpdm. It will be very helpful for the WPDM customers of Pantheon.
Thanks