Bookworm,
I'd like to see where in PANS-OPS that's described (I'm not challenging you, aterpster).
Where indeed? You know how difficult the relevant documentation is to read, you've commented as such in the past. It is a case of joining the dots. But there are statements relating to hold buffer aeras. My take on these things is that the very mention of which makes it absolutely obvious that the expectation is that aircraft are to remain within.