Not harsh at all, I have a pretty good sense of humor and respect your opinion even though I might not completely agree with it!

You make good points, but I'm not entirely sure we have the same scenario in mind.
A Birkin probably wasn't the best item to use in my hypotheticals, since some seem to be expanding the discussion by raising points that are factual, such as a Birkin being up for grabs and not on any waitlist existing highly unlikely. I wish I had made it a Bearn wallet, so it's less stressful for the mind to imagine the scenario rationally.
If I were a new customer and I really really really REALLY loved an item which someone else had already committed to buy, I would just be patient and wait for my turn. But, if the other person wasn't even sure of buying it, then by golly, yes, I think it would be unfair if I couldn't see it or buy it. I will go home with my lovely orange Bearn, goddammit! TODAY!!!
If I were a loyal customer and was interested (key word: interested, NOT CERTAIN of buying) in the orange Bearn wallet that had just come in, of course I would be disappointed if someone else snapped it up before me before I could see it. But I wouldn't hold it against anyone. Not the SA, because it wasn't a pre-order or waitlist item for me (key words: pre-order or waitlist, SURE of buying). Not the new customer either, because maybe it was just her lucky day. I'd be disappointed at first, yes, but ultimately, I'd be okay with it since a.) I knew I wasn't entitled to the item since I didn't commit to it and that b.) it probably made someone else's day full of joy and c.) created a possibly long-lasting and rewarding relationship between my SA and a new customer. (Wait, not sure if more competition is a good thing... Hehe!)
(Hopefully, no one will be responding with "Oh but stores usually carry more than one Bearn wallet, so that can never happen." LOL!)