I am having the same exact issue. I thought the reason might be because my customized version which has a 1.7 Ghz Core i7 is the same processor as the mid-2013 models. However in looking at some other posts online people with customized versions that have 8 GB of memory are having the same issue, even if their processor is the 1.4 Ghz Core i5 which is only included in the early 2014 models.
They Early-2014 Models came out on April 29th 2014, and looking at my serial number you can see that my computer was made AFTER that date.
There are however computers that show do Early 2014 such as the MacBook Air in this unboxing video.
https://www.youtube.com/watch?v=hjkrv2-kwCs
What's interesting is the computer in the video was made BEFORE mine (from the serial number) yet it shows as newer in Apple's system
Now I have seen some posts indicating that apple will fix this issue via an update, however it is NOT just a software issue but also an issue in Apple's computer systems
If I look my device up on https://selfsolve.apple.com/agreementWarrantyDynamic.do
It shows as a mid-2013 Model, whereas if I look up the MBA in the YouTube unboxing it shows as an early 2014.
I really hope Apple fixes this, I have spoken with managers at two Apple Retail stores and they offered to exchange my device within the return period, but I have yet to have gotten a chance to head over, I will likely within a day or two.
