Prime Exclusive Discount suppressed- Seller support uselsss

We have a suppression notice on some (but not all) SKU’s when setting up a PED which I have never encountered before which states:

“Suppressed. Ineligible disbursement reserve policy”

When we click on ‘learn more’ nothing happens (great UX Amazon, thanks).

We contacted seller support and got a standard alphabet spaghetti template response, which of course we just receive over and over again if we ask for clarity. That non-sensical response reads as follows;

“I want to inform you that you are facing this error because this is a mandate in EU and we do not support an exception process in UK, sellers would have to wait till September before everyone is migrated to DD7 reserve policy and sellers will be unblocked from running prime discounts”

What on earth does this mean? Why can we run PEDs on some skus and not others, even if in the same category?