What you seem to be completely oblivious to is that the external circumstances, once you're in custody, place you at a serious disadvantage. Probably the major point about why you should only talk when and if you want to is that to give answers that have any semblance of truth to them, you must be controlling the circumstances. It's very easy to say things that will be taken to mean something entirely different from what the truth is, when you're under pressure/duress (interrogation just after arrest, etc.).
So, what are the positive outcomes? One positive outcome is that you'll not be asked about stuff in the heat of the moment, and you'll have your lawyer present. Your lawyer will direct you to be specific and to the point so that you don't say things that can be interpreted to mean what you didn't intend.
In other words, you're completely delusional in your belief that human speech is something that has only one meaning, and you're similarly delusional in your belief that you have full control over what you say. Sorry, it doesn't work that way. You are most definitely not in control of what you say when the external circumstances are set up for you not to be in control. When you are arrested or interrogated, you're interfacing with people who are trained to extract the information they want (not the truth!). The positive outcome you're looking for is that by 5th letting you keep your mouth shout you won't implicate yourself in stuff that you didn't even have any idea about.
Basically the whole idea that you're telling the truth is flat out wrong. You think you're telling the truth, but still you will be guided to say it in such a way that it'll be taken to mean precisely what you think is false. Remember, you're dealing with people who don't arrest you to have a chat with you. Once you're in custody, nobody presumes your innocence until you get into the courtroom. It'd make no sense to arrest people who are presumed innocent by the police or prosecutors. Nobody does that. When they arrest you, they think you're guilty, and their job is to prove your guilt in any legal way, and often in any illegal way that you won't object to.
You're naive beyond belief.