Hi @John Steele ,
ReFS support for the File Server Resource Manager (FSRM) has been a feature many have been requesting for some years now, I haven't heard anything official from Microsoft regarding this, there was a uservoice request about this but since Microsoft is moving away from the uservoice (feedback) platform it is now down so we cannot view it.
You could send feedback and check if there's any plans on the ReFS support by using the feedback button at the bottom of the FSRM documentation pages:
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