Registering in CommonProxy?

On the pages for both Items and Blocks you state that registering is to be done in CommonProxy. But I thought that this is no longer the case and you can subscribe to the event anywhere?
Mind you while I used to be a programmer, my brain has problems with OOP and I tend to think Procedurally, so i could be wrong in my understanding? Thing is, I try to learn all this but every tutorial I look at and all the source code I looked at, seems to do things differently. Which makes it even more confusing. Differences between versions doesn't help either :(
Anyway; could you clear this up; does it need to be in CommonProxy or not, and if not perhaps change that on the site?