@Nick Sieraad Thank you for posting your question in Microsoft Q&A, apologize for any inconvenience caused on this.
To this behavior, I have created a consumption-based logic and followed the documentation steps and able to retrieve the Get Parameter value in the browser while requesting the call back URL.
- If you enable Asynchronous response under Networking for response action, then you will be the above shared Json which is expected instead of the get parameter value.
- If you want to project the Get Parameter value in the browser or in the output while requesting the call back URL then you need to disable the Asynchronous response.
Hope this helps, let me know if you have any further questions on this.