My preference is to put wet supers under the brood, rather than above a crownboard with a tiny hole. Underneath, they think its IN the hive, just in the wrong place, so they tidy up. No great fuss. My only problem is needing help to lift the stores-heavy 14x12 broods OFF the shallows when the time comes!
But with the supers placed above, you are trying to convince them (by the small hole) that it's actually outside the hive -- which is when the recruits start looking around near the hive for this free honey to "rob". Unfortunately, it can lead to real robbing --- BECAUSE the dance language doesn't have the vocab for "just up above", only "its really close to the hive".
Leaving them out for whatever passing bees to open-feed on is every bit as daft as any other open feeding.