Changing a hitbox takes like five seconds, it's a value you can simply alter, you don't have to add anything, and that's a very common change fighting games make in patches.
"The absence of evidence, is not the evidence of absence" applies to your claims here. NRS not saying they made something deliberate does not prove it wasn't, it's not even evidence one way or the other, it's evidence that didn't say anything about it. Otherwise, I apparently have "proof" about a lot of unintentional stuff in the game, such being able to change the block advantage of Erron's coin shots by shooting your opponent closer to the ground, in fact I have more "proof" of that than this ice clone business, because the menu frame data says coin shot is like -12 or -14, and that's it. Except, again, it doesn't matter, it makes that move have a point unique to itself, and intentional or not, it's in the game. Again, Sub's clone "issues" do not make him bad in anyway, he's still extremely good, the only difference is, now you are rewarded for properly spacing yourself, and punished for improperly doing so.
The point of whether it's intentional is a moot point, completely unrelated to if the game is better or worse for it being in. That is the discussion that should be happening, whether Sub is made more braindead with it fixed, does he need it fixed to be competitive, etc, because those are actual discussions that matter and can produce proper suggestions to NRS to improve the game.