What is your source. Considering Bungie has not released any info it yet apart from the stuff in the thread, we will have to wait for teh beta in late spring. Even then it will not be very rough and sketchy. only on the release date may we understand it's full power.
Got this from the easter egg site from red.-
There are three confirmed grenade types: Frag, Plasma, and Spike Grenades. In the Et Tu, Brute, four grenade types were seen, however, the fourth grenade has not been confirmed. However, Frankie has said that it is not the shield grenade and that the fourth grenade might not make it into the final game at all. The bar that tells you how much of your shield you have left seems to have been moved to the top of the screen and centered.