Gram Demolition and Dispersion

[nr42]

The fact that he doesn't have to hide the ability since other people can use Gram Demolition.

This... Gram demolition is known by many and he isn't the only one who can use it.
Gram dispersion on the other hand is not.

Think about how much attention it would bring to him if everyone found out he could use Gram Dispersion (definitely not in the Yotsuba's plans). I think this is the reason why he played it off as mist dispersal (not sure if the name is correct, but the one that breaks down molecules rather than the information) when he had 16 air bullets flying at him

Mist dispersal is just as classified as Gram Dispersion. That's why Cardinal George threw a hissy fit in v7 when Tatsuya used it around his hand, whilst chopping of someone else's.
On the air bullets he used Gram Demolition. Once the magic holding an air bullet together vanished so did the air bullet (since it was a bullet made of air ) but he had to throw 16 "masses of compressed Psion particles" in a short period of time and therefor failed.

[Zuruumi]

Well Gram Dispersion is quite similar to Mist Dispersion (as was already pointed out there). The only difference is, that Gram is against magic and Mist is against physical target.

[nr42]

It's basically the same magic, since he reads the structure through the information dimension and then disassembles it.