I wanna play a COPY_OF_Warlock. Or maybe i'd rather play a COPY_OF_Warlock.

Yeah, what is the deal with these? Anybody know?

At a guess I assume it's part of their testing to implement the Class Variant Features from the latest Unearthed Arcana. 

You are far from the truth there...

those would appear on your list of classes if you created subclasses !
those would be your actual "in your collection" homebrew classes. unless you deleted your homebrew classes or renamed them, what you see there probably is your homebrews.
if not then i don't know what to say. but i really doubt it is them, they have their own servers and testing gears that do not ends up on the official site.

Quote from DnDPaladin >>

You are far from the truth there...

those would appear on your list of classes if you created subclasses !
those would be your actual "in your collection" homebrew classes. unless you deleted your homebrew classes or renamed them, what you see there probably is your homebrews.
if not then i don't know what to say. but i really doubt it is them, they have their own servers and testing gears that do not ends up on the official site.

 You can't make homebrew classes though. And subclasses don't have their own spell lists.

Quote from DnDPaladin >>

You are far from the truth there...

those would appear on your list of classes if you created subclasses !
those would be your actual "in your collection" homebrew classes. unless you deleted your homebrew classes or renamed them, what you see there probably is your homebrews.
if not then i don't know what to say. but i really doubt it is them, they have their own servers and testing gears that do not ends up on the official site.

 
It is possible I am far from the truth but as DxJxC has pointed out: you cannot create copies of classes. So if this was Copy of Shadow Magic or Copy of Trickery Domain I'd agree with you, but it's showing as copies of a class. Also, there have been instances where I've seen things like this (Copies I did not make, did not have in homebrew, and was not in any campaigns at time) and eventually disappeared and it turned out to be the devs testing things, which is why I think it may be the case here. 

Quote from DnDPaladin >>

You are far from the truth there...

those would appear on your list of classes if you created subclasses !
those would be your actual "in your collection" homebrew classes. unless you deleted your homebrew classes or renamed them, what you see there probably is your homebrews.
if not then i don't know what to say. but i really doubt it is them, they have their own servers and testing gears that do not ends up on the official site.

 How can a user make a COPY_OF_Warlock, or Cleric for that matter, when users can't copy base classes?

I think you're confusing it with the fact they're seeing this in the hombrew menu, probably for making a subclass.

 If I try to filter via class on the subclasses homebrew I don't see any of the COPY_of versions - but I do see Artificer2.

I bet they are for testing. The homebrew tools are the same tools the devs use to add stuff, just with some options hidden/turned off. I bet these just accidentally get through.

the thing is, i dont think they are using the official website for testing purposes, i think they have a secondary website to do that and thus these wouldn't appear.
but since Eberron is coming and the class feature variant UA is there... i'm beleieving these ar eleft overs that shouldn't ahve made it to the official websites.
i'm also thinking they are the UA thing. after all, because of it, they have no choice but to allow us the ability to change core classes now.