Missing the point...
OK, it's a good, funny take on things, but also misses the point a bit of the challenge the retailer has.
Stock levels are never perfect. In reality, these stores will have just enough stock to satisfy the majority of customers. Stock will be in a number of places independent of the number of stock rooms - could be in the stock rooms, on the shop floor being tried on, or on the shop floor as an example of the item, as well as on the way out of the store, or on the cages coming into the store. This overlooks the inevitable 'shrinkage' that occurs in retail (or theft as it's known elsewhere) which mucks things up. So, when someone says have you got a size x in that shoe, this is not a simple look in the system and 'yes' response. It will be more of a 'yes, there's one somewhere in the store, but I can't tell you if you can have it or even look at it as someone else might be either buying it, trying it on, sending it back because it doesn't fit, or it's not really there as someone has stolen it'.
This is further compounded by having a vast range of items on show in the store and each item can come in a range of sizes, and a limited amount of space to store them in. Once again a compromise has been considered here in terms of the range of items to show as available and the reality of keeping a full stock of all of these items in all the sizes, which simply comes down to front of store space vs back of store space. And I guess the outcome that's generally decided upon is to have a larger front of store space to show the range of products available, even if they can't carry all the sizes of each one.
So, I doubt that the walkie talkie system is there for any other reason than the good folks that have done the T&M studies on it have found it to be highly effective, requires minimum training for what will inevitably be a high turnover of staff in the stores.