Yeah I thought as much..
I’ve had a thought about how I can achieve this via the UI.
I have at the moment a field group called Blocks and it’s being cloned into a flexible content field.
I’m thinking I will have two seperate field groups, Parent Blocks and Child Blocks, with the child blocks being empty.
I assume the parent will be overwritten the second I save the child blocks field group and it will merge the two together in the flexible content clone.
I might mess about with making the parent blocks being private, I’ve not tested that.