You can discuss word order and context until the cows come home, we all know that overloading a mana crystal regardless of how it happens should trigger unbound elemental. Anything else is just a level of nit-picking from team 5 that is not evident anywhere else in the game. Shamans have it hard enough without this bullshit.
No actually, English reading comprehension dictates that we know it should not work. So everyone who thinks they know, is simply wrong from a literary standpoint and maybe should go back to school.
I agree there's no reason for it not to synergies, however, the wording makes it clear it should not work in its current state.
It seems like you are just looking for ways to insult people, an aspiration that was doomed to fail when you tried to apply the term "literary standpoint" to a Hearthstone card.
In fact, the rules of English do not give us any insight into the game's definitions. In fact, by any reasonable application of the rules of English, Guidance is a "card with Overload," as it is a card, and it does have "Overload" printed on it. Arguing against those facts based on the syntax and semantics of English is simply ridiculous.
However, because Hearthstone does not explicitly define terms like "Overload card" and "card with Overload," there is actually no way to know how cards with vague wording like Unbound Elemental are going to interact without trying them out. You may make an educated guess based on other Hearthstone cards with similar wording, but you cannot possibly predict the exact interaction based solely on the rules of English.
At any rate, what we've learned from these two cards is that, as defined by the game, "card with Overload" seems to mean exactly: "card that causes Overload whenever it's played," not just sometimes, and not at the player's discretion.