on the other hand
On the plus side sending the machine to Apple does mean that the spent batteries will be recycled 100%. We may see over time that these battery replacements could be done in store - that would be idea.
There are advantages to having the battery inside, less casing, better protection for battery and more reliable connection between battery and device. Given that this sort of servicing only needs to be done every 2 -3 years and that many laptops, even with replaceable battery are discarded without ever replacing the battery, it kind of makes sense not to have the battery removable.
Regarding article, it should be also noted that the Macbook Air also consumes much less electricity than a comparable laptop.