I have a doubt.Could they actually take out the contents from an original perfume.Lets say they empty half of the perfume from the original bottle and then they add some cheap alcohol(not the alcohol we consume, ones used in perfumes itself) to fill up the bottle.Then they carefully pack the perfume(with all the cellopane and cover)and send it to the customer.This way the bottle smells of the original perfume, but its weaker.That is its longevity and projection is affected due to the dilution.
If its not this, then the other thing they must be doing is that they are selling expired stuff.
I have in the past bought from them several perfumes.Some smell genuine while others seriously don’t.