To answer my own question, the spark propertery is not required.

What is required is for you to use the access point alias, not the configured "name" or "arn" as detailed in the Spark documentation.

Read the access point https://docs.aws.amazon.com/AmazonS3/latest/userguide/access-points-policies.html documents very carefully and make sure to add the access policy permission set, as well as the role that you have defined in your profile instance.

This should be a better documented feature in the AWS Databricks documentation.