I do not see why anyone would use this card. Unupgradedly, this costs 6 quanta while black hole only costs 4. This requires an duo element, while black hole is mono. This has a turn delay before it's ability can be used, while black hole is cast instantly. This refunds 12 quanta to the opponent, while black hole doesn't give refunds at all. Both cards require gravity.
Ninjamaster has already answered your question, Vara (thanks ninja). The card's main function is one-time healing. The effect of Black Hole only plays a role *if* your opponent has quanta in two or more elements, though it is still limited. First, he will gain a nova/supernova, you're right, but it will not benefit him/her in any way, as it will be drained the very moment it is cast; that is where the healing effect comes from. As I said before in the spoilered note section, it
can be used as a form of quanta control, but there are more efficient ways for that - the unupgraded version can drain up to the maximum of 2 from each of the opponent's
original quanta, while the upgraded just a single point from each. The relatively high cost of the card is based on these two combined effects, and Entropy's possibilities in mono settings. You'd need a highly specialized/dedicated deck to bring it's quanta-denial to a full effect.
Does it needs rewording? I'd think it's pretty self-explanationary, but I can try, if it's not clear enough.