EastCoaster,
I'm in complete agreement with Tinstaafl that there is no ambiguity in the example you've given, nor are there any grounds for confusion as it's such a common clearance.
Alexban does make a very good point that the better control instructions would include an EXPECT advice, so that the pilots can plan accordingly.
As you "Just wanted a little perspective from the other side of the fence", here's 2 considerations -
(1) If it is ATC intention that the aircraft may have to hold (which you've alluded to), there is a significant difference between the aircraft speed and configuration for holding, and that for approach. Holding will generally be clean or at a low-drag flap setting at a relatively higher speed, preparation for approach entry will probably be with intermediate flap settings at somewhat lower speeds.
(2) Whilst many aircraft have separate Localiser and Glide Slope arming functions on the Auto-Pilot / Flight Director, or separate Localiser / Approach arm functions, many aircraft only have one single Approach arm function which implies that the aircraft may not be armed for Localiser capture alone, without also arming the Glide Slope function. (This does not excuse pilots for making an uncleared approach, but might explain why they're angling for full approach clearance). In this latter case, 'establishment' on the localiser may only be accomplished by using secondary modes (Heading and 'raw' Nav data) rather than the full AP / FD capability.