Thanks for clarifying. I do not see a workaround. This Zap, in Zapier itself, indicates it works for email addresses specifically. It gives no indication that it will accept ID or a custom property value.
In this case, adding your suggestion to the Ideas Community and getting some upvotes will be very helpful in getting your suggestion in front of the Product team. If you add a link back to your Idea post, I'll be sure to give it an upvote to help get the ball rolling.