Yes, letting the leaves break down at the base of the hedge is certainly compounding the problem. Your hedge could well have two diseases — bacterial leaf spot and fungal shothole.
The hedge should be strong enough to outgrow them, provided the growing conditions are improved.
As the prunings will also have the disease pathogens active on them, leaving them on the ground will lead to the disease spreading back into the hedge.
By all means compost the prunings but ideally in a compost bin, in another part of the garden.
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