I kind of agree and disagree on this.
Often in the Suttas the Buddha talks about the first 4 precepts when discussing Right Action or bodily Sila. And the 5th Precept doesn’t get a mention. So yes, these first 4 are super important and a major role of Precept 5 is helping us with our Right Action.
But I think the 5th Precept also has a role to play in a number of other factors of the 8 Fold Path.
Right View: There’s a difference in oneself when one views this precept as being important and when one doesn’t. It’s a view that changes our relationship to other Path factors.
Right Intention: I think this is often overlooked but is just so important. It’s part of the intention of Renunciation. The type of thing where one is growing away from the Sensual Realm, from kamaloka stuff and is instead growing into the mind’s joys and clarity more. Really, all the precepts are about this; all harmlessness is about moving away from the coarse, about letting go of that which is grosser; the beginning of a movement towards that which is more refined, more delicate, more sublime. A letting go of ways of being in the world that makes us denser, more stuck more ignorant.
It’s part of the other two aspects of Right Intention also, because it’s an act of kindness and compassion to ourself and the world.
Right Speech: Well this has to be obvious. Particularly when someone is inebriated. But also, I find, when someone isn’t. This is going to be controversial and I apologise for any offence caused but I’m just going on personal experience; it’s much nicer to be talking to people when they don’t have even one drink anywhere near them. It’s like the vibe in the environment changes or something. Perhaps it’s just me. 
There are people in my life that I love and admire who still drink…so I’m just going on how I feel when relating to them and comparing them with one drink in hand, lots of drinks and no drinks.
Right Effort: The effort to understand the place of this precept in your practise with gentleness and forgiveness and peace.
Right Mindfulness: Obvious. But it’s not - for me - just about not getting inebriated. It’s about a deep affirmation to myself about my whole hearted commitment to shy away from anything that has even the potential, to cloud my mind. Now, having said this, I’d like to be clear that I’m a dismal failure in most regards. eg. I watch too much t.v… However, it makes me feel joyous to know that I will not, under any circumstances feel pulled by any desire or perception of pleasure to drink alcohol. …to the t.v yes, but alcohol no… I’m hanging out for the day when I have more t.v mastery…or rather, a lessened perception of pleasure around the t.v!
Right Samadhi: Again, obvious and closely related to the previous factor but I think also, very much related to Right Intention and growing away from the realm of the 5 senses into the silent, still places of the mind. Clearly, anyone still watching too much t.v. is still very much working on this one! Thank heavens for 8 precepts and retreats and stuff like that!
In my humble opinion there’s more to the 5th precept than initially meets the eye. Growing mindfulness in the here and now is important. But a more whole hearted commitment is also about understanding the value, beauty, gentleness of sense restraint; even though we may not still be able to keep such restraint purely.
Oh…sorry this is such a long “comment”…