Was expecting Miyao.
Disapointed.
But for real hyperflexibility doesn't save you if they have good control of the joint being attacked, just means they have to crank through a broader range of motion before the snapping/tapping begins. It does give you more wiggle room to retake control though.
When I've seen people "immune" or more accurately highly resistant to specific submissions it was more commonly a muscle issue than a hyperflexibility issue. Necks like a tree trunk as thick as their skull, tree trunk legs that could hold the boot through everyone's ankle lock, arms that can bench press your americana attempt, etc.
Toe hold is doable, though you may need to keep rotating and grip changing like you're trying to spin the spindle door handle on a submarine hatch / door.