AWS Comprehend with step functions not returning success

Question

Using AWS step functions Comprehend:CreateEndpoint together the wait for callback like so:

arn:aws:states:::aws-sdk:comprehend:createEndpoint.waitForTaskToken

The above step succeeds in creating the endpoint for a given model version, but does not return success / failure response that then moves to the next sfn step.

Am I misunderstanding waitForTaskToken or does the comprehend api not support this (how can I check?) Finally, is there a simple way to implement a wait until endpoint created then move onto a classification step?

Edit: I see now that there is a .sync functionality for optimized service integrations. This is what I need to achieve, but it is not available for comprehend as yet afaik. Simple way to mimic it perhaps without a getStatus / waitXseconds pattern?