No. The All Metal mode is not a true all metal mode as it is still a processed mode that only accepts all metals, and it carry's the same depth all other coin modes do.
The only concernable tone and segment difference you should find between All Metal and the Pattern Modes, is that the Pattern Modes will start miss-placing some junk targets into segments until you do a quick Factory Reset. I've noticed most of my units will start miss-placing around the 30 minit mark if notching is brought into effect with sensitivity high, whereas All Metal will take a few hours most days before a Reset needs to happen.
The Ground Balance mode is a pure and full All Metal motion mode and runs very deep. As you're a 'listen to it all hunter', try the Ground Balance mode on your relic hunts when you may feel outright depth is warranted, and switch to Coin Mode over targets. It won't pick up the deeper ones the GB mode will though.
Do give multi tone a go, in All Metal, an open disc pattern, or a slim pattern. We probably nearly all laid off it at the start, due the whole pinball effect, but that dissapears real quick and you tend to isolate and judge a target quicker with it.