In the following video this monk said that consuming alcohol is a latter addition to the fifth precept and hence not part of the Noble Eightfold Path. I wish to know your thoughts on this.
Without watching the video, I think it is a late addition.
It apparently wasn't among the first of the Vinaya rules either (see this origin story).
I do think alcohol is problematic though, in my experience: better to avoid it.
The custom of asking for precepts, and most explanations about them, and how to train, including all the factor things, are later developments: to sort out something easier to catch by many, even not having found the prerequisite of right resolve.
Instances where the Buddha counted all five are few. Mostly he would speak "only" about the first four, since those are the "real" outwardly actions. Yet he did also often point out the drawbacks of intoxication: it is intoxication which is actually the obstacle, the antidote of right resolve, and it has many layers. He therefore was in all ways eager to encourage on the subject of intoxication: and since (with intoxication) it is not possible to gain right resolve or to have right resolve, it is clear that intoxication is an obstacle for the eightfold path, the most gross: by taking physical food to maintain such.
As for the Silas, conduct that at least provides possible best relations and security in a community, they are not only given for gaining the highest goal, since the Buddha knew that very few beings would strive for it.
If seeking this virtue within the four precepts, one actually finds it in the 3rd: "Kamesu", later "Abrahmacariya".
One also does not find it directly in the main precepts of monks, which also display "only" the four. But again, intoxication, gross or subtle, is always the root of transgressing the basic four.
Look here, who much breaking of the precepts is done but intoxicating with becoming and being on BSe. The more people are addicted to it, use such a substance for relaxation, the more they tend to real worse thing.
At least intoxication makes crazy, and is the cause of an existence of being a fool and/or have crave mental lacks.
So for a virtuous lay-person, following the Buddha, wishing to attain the path within, not only at the end of ones live, having a secure dwelling and most secure future destination, indoxication, that causes heedlessness, lack of conscience, has to be avoided. It's part of the duties for lay people, is sad in the Dhammika ("Buddhist") - Sutta, and of course, a person having entered the stream whould not deliberatly indoxicate himself, in a way that it becomes root for breaking the precepts, would not give deliberatly signs of approve indoxications as well.
The linked Sutta should possible cut away the believe that the Buddha approved indoxitation for what ever aspiration within his Sasana, good wandering on, avoiding downfall or liberation, all paths in this world, following him.
And, being indoxicated, it is not possible to gain path or fruit, therefore, avoiding the indoxication with means which cause heedlessness, is part of the Noble Eightfold Path for having delivering effects.
(Possible later edition on the answer, as well as space for further questions and discussion, is given consciously here.)
[Note: this is a gift of Dhamma and not meant for commercial use or other wordily gains, also not for getting indoxicated but to become sober and gain release.]