Hi Lihi,
Thank you for your patience.
We have validated our source thoroughly and the grid retrieves the UI element using AutomationInteropProvider (CodedUI automation elements) only whereas, the FlaUI does not use the System.Windows.Automation.Provider library. So, we regret to let you know that the GridGroupingControl does not have the support for FlaUI and we do not have any immediate plan to consider this in our feature list as the GridGroupingControl is considered as classic control.
Please get back to us, if you need any further assistance.
Regards,
Arulpriya