Brimstone
Good point, and well put.
But what if the centre-fix were an actual named position, which had been determined (by whatever means!) as the point at which your average pax-carrying a/c will intercept the 3deg GS for the ILS App? And what if it also happened to be a published VOR/DME hold? Both of which pieces of info were well known to regular users!
Unfamiliar crews I can understand encountering some uncertainty or being possibly a bit confused, but it appears to be more a case of regular users involved!
With reference to what you said, any instruction to route to the centre-fix that I've ever heard have been after a crew request, and in common with your operating procedures, the position of that centre-fix has been determined. It usually turns out that it's actually not a million miles away from the published position!
The instruction from this end always uses the name of the published position, I used the term centre-fix myself for simplicity sake (guess that wasn't so clever!).
I can see where you're coming from on this, and it is actually quite rare that the flight would not be cleared for the App on establishing, but it is always better to be careful and to keep at least one trump up your sleeve, don't you think, rather than ending up with egg on your face and having to cancel a previously issued Clearance, or worse!!