The idea has been around for yonks. I have tried it but, while it might work in drier areas, it doesn't seem to work here. Once the fleece has been flattened by rain, and has a wet surface, the slugs and snails aren't bothered.
As YorkshireLass says, the soil can become unworkable, especially if you use a rotavator or mantis, as the fleece, when unrotted, becomes tangled in the blades. So overall for me it's a nono. It's quite useful for covering the compost heap if you have felted fleece. It reduces the rain and keeps the compost warm and working. When you use the compost keep back the fleece and use it on the new heap.