Seraph said
He can use a partial release of 1/3rd of the full seal, so tell me exactly how having this technique is so bad. It increases his strength and speed temporarily, that's all it does at this stage. You act is if he has full control of an S-ranked tech and learned it himself, it's a tool for developing his character.
It's just not really a favorable technique no matter how many limitations you place on it.
It's like giving a Genin a Mangekyo, but saying it's chakra exhausting, he's blind all the time, he has no other releases, and he can only use it at certain times of the day. Even if you put limitations on a fairly powerful power and give it to a fairly inexperienced character it just looks awkward. The technique is bad because it is not good. I don't think there is any reasonable excuse for the character to have it, personally, and I think a lot of other members are in agreement.
It just is too awkward and, no matter how well you tailor the bio and the explanation of the ability, doesn't reasonably fit.
That's just my opinion on the matter.