i thought pos aren't really an "order" yet, until it is approved by paris, hence they can only "cancel" it after the order has been placed by the sm (not the client).
According to my sas, whom have explained the whole podium process with me quite clearly. (things can differ a little from country to country, but i think the general picture is the same)
1) regular clients submit/express their "wishlist" to the sms before they go off to paris at each podium. But you don't have to do it in jan/jun, you can tell them i really want x anytime, say in march (just after the feb podium), and the sm will just have to note it down, and then order it at the next podium (july), so the wait to see whether this order has been approved is, of course, a lot longer than say, if you have told the sm in jan. At this point, this is still a "wishlist", not an "order". I know people like to say that "i am going to order this and that", but bare in mind, nothing is an "order" until paris has approved it, before then, it is still your "wishlist".
2)the sms take this wishlist to the podium with them, and see what's availabld to order, then match this with the wishlist and submit their orders for the next season. (feb for aw, july for ss)
3) once these orders have been approved by paris, they will become an "ordered book/list", which are all the items that the store will/should receive for the entire coming season. Hence, everything on this list is "approved", so if your item appears on this list, then it is now an order. So your sm will be able to tell you whether the item you have asked for has been approved or not at this stage.
4)as you can see, this order list is for next season, so there is at least a 6month wait for whatever you've ordered. Some people said they've only waited a month after they have submitted their "order", but to my understanding, it is not the item that the sm has ordered for this client at this particular podium, it is merely an item from the current or past season, which hasn't been spoken for, and has just arrived and happened to match the client's "wishlist", hence, was offered to this client, so she didn't have to wait for the one which the sm has ordered for next season to arrive.
5)sometimes, things that the sms have ordered just never arrive at the store for no reason, some are actively canceled by paris, some are delayed for more than 2 seasons.(aka pending orders from previous seasons) so i guess, you can call all these scenarios as an order being canceled by paris.
6) clients are generally told that pos take 6months ~2 years to arrive, because the order can be delayed for many seasons, but most of the stock should arrive within the next season
7) special order is a totaly different route, and hence whatever i have written does not apply to sos.
8) every country has a different policy for their "waitinglist" or "list" (however you want to call it)
a) some store let a very small amount of client to choose from their ordered stock list for the coming season, (but you can only choose from certain colours/leather/size/hw) so the chance of getting what you have chosen is very high.
B)some stores from time to time ask their clients what they want, and keeps a list of client name with their "wishes", and may use this as their guide at each podium, but you can submit your wishlist in ss11, but sm might not have ordered it till ss12, so you dont' know how long you'll wait for this item. Not everyone can go on this list.
C)some stores (like taiwan) let everyone put their wishlist down, you don't have to be a regular client to submit your wishlist. It is a merely a record of clients who wants b/ks. They don't use it to make orders at the podium, it is not an order list, not a waitinglist, it does not mean you will get this item for sure, it is just a client list, just in case one day a vip turns down a bag that the sm has ordered for her, the sas will then go to this list, and call those who also wanted the same bag.
9) can you change your order once it has been placed at the podium? I am not 100% sure about this, but my guess is no, once it is ordered by the sm and once the sm has left paris, it can't be changed. But if you are lucky, if there's something else that matches your criteria in the same poidum ordered list, and hasn't been spoken for, then the sm might offer that bag to you, or if you are a vip, they will re-order it for you at the next podium.
Ok, keep in mind, this might not apply to all stores and even whatever the sm has ordered, might be altered by paris without prior notice. (ie changing the hw, or the size or the leather etc)
Or I could if there weren't so many other ones in the closet. 
