As far as I know a raft is used to help hold a small part to the bed. This I guess was and issue back in the day when printers were not very accurate, heated beds were not main stream and there was not a lot of quality filament? A raft puts down a bed of filament so the small part will stick to the filament raft better than the bed surface. PETG will stick to most bed surfaces too well.. I have had it remove chunks of glass from the bed when the part was removed.. so It just seams very strange to use a raft for petg.
A raft is normally multiple layers thick so you can get it off the bed and then get the part off it it. A raft is just that a raft of plastic the part is printed on top of. If it is only one layer thick you are going to have a problem getting things off.

There are normally slicer settings that control how tightly the part sticks to the raft (separation distance)