He already explained that the expectations are wrong to begin with.

2013 models had drives from different manufactures and some of those were slower than others.

Here's an example: Say 2013-A-SSD > 2013-B-SSD and we have the same two A and B SSDs in 2014 machines.

Then 2013-A-SSD > 2014-B-SSD.

With just one machine (and without knowing the specifics) you can deduce from the above that "2014 drives are slower than 2013s" when in fact they are the exact same 2 models that 2013 Air's had.

Which still means that, if you buy a 2014 model, you might get a machine that's slower than the 2013 model. It's not always the case, but it _can_ be -- which, as a prospective buyer, is infuriating.

>Which still means that, if you buy a 2014 model, you might get a machine that's slower than the 2013 model.

I think what you mean is "You might get a machine that's slower than _a_ 2014 model". Assuming every 2014 model performs at the baseline, unless that baseline is lower than the previous generation's you're still getting better performance than the _official_ 2013 model.

And which model is the "official" one if not the one that I bought in the Apple Store? There is no official and unofficial one, they're all sold under the same name.

If I have a 2013 MBA I expect the SSD when I upgrade to a 2014 one to be at least as fast as the old one.

OK, let's put it this way: Apple doesn't guarrantee you a specific speed, and doesn't tell you you'll get a specific SSD model in your Air.

It just tells you you'll get a speedy SSD of X capacity (true), and you're not supposed to obsess over manufacturer and a couple percentage points of performance. Else, you wouldn't have bought the Air, but some custom rig.

What expectation? Apple tech specs are very brief for the ssd drives, just size and 'PCIe based', and they have a nebulous comparison to a spinning drive. They also don't tell you what model processor you get, just family and speed.

The expectation is that a 2014 model will perform at least as well, if not better than, a predecessor model from 2013.

That's a perfectly reasonable expectation to hold, as well. One really shouldn't end up worse off (for whatever reason) merely by buying a more recent model, especially when it's a computer that's being purchased.