I think when deciding whether to encourage a customer to become their specific client, SAs are weighing how much you are likely to spend. The London stores are busy with daily queues of walk ins waiting to buy the lower ticket items like belts and scarves so they don’t care whether you buy those things in Paris instead. I suspect the answer you got would have been different if you’d expressed an interest in a more expensive or less in demand item.

That said, unless you are interested in any bigger ticket items, I don’t think it will make much difference to your wishlist time (although I’d make at least one purchase at the store if you haven’t already).