Ahh, that seems problematic. In the JS SDK i can only publish to a topic via ARN.
Ok thank you for the full explanation, i’ll use the join for now :).
I’ll also see what resources in the AWS space are available to help out here, from an outside perspective i would assume GetAtt should be able to get an Arn if the resource has one.
I figured this out using Ref https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-ref.html which will get you the sns topic ARN 
Thank you!