@Darragh Martin, Thanks for posting in Q&A. From your description, it seems you want to onboard MacOS device to Microsoft Defender for Endpoint instead of enrolling into Intune. But from the picture you provided, it seems the devices are enrolled into Intune and managed by Intune. Not go to Microsoft Defender for Endpoint. If there's any misunderstanding, feel free to let us know.
Based as I know, to onboard MacOS device to Microsoft Defender for Endpoint, there are manual methods or deploy via Intune:
For Bulk onboard these devices already enrolled into Intune, you can follow the steps in the link below:
Hope the above information can help.
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