Could they really be this complex about it?
If yes - there is a certain genius to this. Even Russians, with their very low opinion of America, would be shocked to learn that the US embarrassed itself to such an extent, just to buy space for maneuver for the Ukrainians.
Also, in this age of satellites (yes, Orcs have them too) and sophisticated signals intelligence collection abilities, it would be impossible to obscure the intent behind such a large offensive action.
The Ukrainians are right - the only ones to win from this leak are the Russians.
However, let's entertain for another minute that this was a deliberate leak, and this 21 year old boy is just a patsy. What would the goal be then, if it can't help the Ukrainians better execute an offensive? I would say the goal would be to send Zelensky a signal. Message of this signal:
1) The Western policy where Ukraine and only Ukraine can determine what "winning" looks like, has run its course.
2) Western patience with Zelensky's insistence on "no compromises", "Crimea or bust!", has run out.
3) Western intelligence agencies are not pleased with a situation where they known more about the Russians, than they do about the Ukrainians. Through this leak they demonstrate that they know Ukraine is concealing the scale of its losses, the issues with discipline, with corruption.
4) Bottom line: the leaks shows to the Ukrainians, that privately, the Americans are thinking some pretty dark thoughts. This should wake the Ukrainians up to the need to be more realistic in their dealings. The year of Zelensky as Churchill is over, and now people ask questions.