Correct, the whole purpose is to make the pistol ergonomic for human beings, not space invaders. I will never understand why the hump on the fullsize models is located where it is. I think that all glocks, stock and modified, are some of the ugliest pistols that have ever been produced. That being said they are fantastic tools that could just use some tweaking in the ergonomics department. If you choose to use the glock for self defense based on cosmetics, these reductions are not for you.
I've done a couple of the bedliner pistols as many of the grip reduction companies use this method. It looks good but needs constant upkeep and is not as durable as other methods. Also, I find the burnt in texture to be more comfortable and more grippy. The new method that I'm using pictured above on the black G21 provides the same asthetics as the bedliner jobs but gives the reduction more strength than any other method that I know of. There are many different ways to go about reducing your grip. To me the only way to go if it's a DIY project is to use the method layed out in these series.