I think I figured it out. I tested exporting a different template (the pencil icon) and I did not have the same issue.
tneilson01
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution
User for
Post
Replies
Boosts
Views
Activity
Hello, did you ever find a solution to this? I am having the same issue. I didn't even create a new icon. All I have to do is download the symbol template, open and save it in Adobe Illustrator with no changes, and try to validate in SF Symbols. I still get the error message. I even tried Inkscape and got the same interpolation error message.