Your research seems thorough, I did the same as I have an a3xelte. Until very recently it was documented here as both a3xelte and a3xeltexx.
The Samsung A3(6) comes in international variants, with stock ROMs which vary by name, implies they are different. Or are they just named so for “commercial” reasons?
Then you look at the device tree, see if the blobs are identical. Software can be built to work with more than one blob. I see the .xx suffix as saying “all purpose”.
The XDA link above talks of “unified” names. After 3+ years of software in service, unified seemed OK to someone.
I still have to wonder if this could have any bearing on why /e/ has a problem building an a3xelte ROM 
as I speculated here.