So, as someone who used to work at Disneyland for 3 years in the late 90's, has worked in sales now for the past 13 years, I think I can make a pretty good guess as to what is going on with the windows in Buena Vista Street. So here is my story of what (probably) is happening:
Once Upon a Time...
First of all, there are three different departments. There is Imagineering, who designed the props, Merchandising, who orders and decides what merchandise goes in what store, and BVS Guest Services, who run the stores. These three departments are not allowed to have any interaction with each other whatsoever.
The executive vice president in charge of merchandise sales sets an arbitrary sales goal that is next to impossible to achieve. After the first quarter of being open (Jul - Sep), the stores don't meet their sales goals. They are given a pass for that quarter only, because they can say that guests were running past BVS to get to Cars Land. After the 2nd quarter (Oct - Dec) of not meeting their sales goals, the managers of each store in BVS that is not meeting it's sales goal is put on an "Action Plan." (in January) This basically means that they have to submit a plan as to how they are going to increase sales, and it has to be something that is different from what they did the previous quarter. Now, the important thing to know is that the managers have no control over what merchandise they sell, and they are absolutely not allowed to say that the reason their sales aren't what they should be is either 1) the merchandise they are trying to sell is boring, or 2) the sales goals are unrealistic. So they have to come up with something like putting more merchandise near the cash registers for guests to purchase while they are waiting in line, or opening the doors that were being kept closed for environmental reasons so that guests don't think they are closed.
One manager of one store submits his or her action plan and says that they are going to display merchandise that the store actually sells in the window, because guests keep coming into the store trying to buy the fake merchandise that is in the window. (This may be true to a small extent, but the manager exaggerates it for the action plan). The 1st quarter of this year (Jan - Mar) passes and the stores still don't meet their sales goals. The VP calls another conference call of all the managers that are not meeting their goals and says that he now has a "Best Practice" to share with all of the managers, and that is they all have to put merch in their windows. So any stores that are meeting their sales goals don't have to do this, but the stores that aren't meeting their goals are now required to do this. It doesn't matter that this hasn't been proven to actually increase sales at BVS yet, the only thing that matters is that they're doing something that is different from what they did last quarter.
So, in early April, every manager of every store that is not meeting it's sales goal is required by an executive who does not work in Imagineering or Merchandising to clear out their window and display merchandise that is actually for sale in the store. Now that summer is coming up, the parks will get more crowded, and the sales will go up naturally, and many stores that didn't meet their sales goals in the first quarter will meet them in the 2nd quarter. This will be attributed solely to the fact that they changed their window displays, and as of the 3rd quarter (early July) every merchandise store in each park that has any kind of fake window display will now be required to display actual merchandise in their window. This will become a standing "best practice", and the executive will get a nice bonus. The managers of the actual BVS stores will transfer the heck out of there and onto Main Street or somewhere that actually has consistently good sales year round, and by this time next year there will be no one working in the BVS shops that even knew that there was a time when the stores had their displays of fake merchandise from the 1920's.
And They All Lived Happily Ever After!