Hunters grounded, and 'vintage' (whatever that means, exactly) jets banned from performing 'high-energy' (whatever that means, exactly) aeros.
Hmmm.
If the CAA had formed an early impression that the 'problem' was with display rules, the concept of a display line, and performing aeros adjacent to built-up areas, they would have brought in rather different temporary restrictions, applying to ALL aeros, or to ALL jets.
I would very tentatively infer from the nature of the restrictions that the CAA knows or strongly suspects something; that there may be an issue with vintage jets in general, and Hunters in particular - and that it's related to the metal, rather than the 'software' or the rules, so to speak...