IFixit didn't reveal 2GB of ram.
We assume it is 2GB.
We don't know what part number "Elpida (Micron Technology) F8164A3MD" is, and neither does ifixit. They told us the part number and said there are 2 of them.
There is no listing anywhere for this part, even in Micron's catalog, and so the only thing we can go by are the benchmark software to tell us
It would be great if Apple listed the amount of ram on the iPad Air 2 spec page.