Initially, one assumes Marco and Jozu withstood Shanks’ Haki…
The general anecdote goes something along the lines of… Shanks boarded the Mobydick with his Conqueror’s Haki activated; some people lost consciousness due to not having the will to remain conscious in his presence, while the others (apparently) were strong-willed enough to remain conscious. Some key details have gone amiss, and therefore contributes and inherently births a misconstrued story. The aim is to point out these missing details, and then give the actual (apologies if this sounds arrogant) narration in light of the actual context.
Before Shanks stepped aboard the Mobydick, Marco and Jozu warn all the newcomers to stay back (away from Shanks), but some being rightly inquisitive felt the need to question pre-emptive safety measures at a rather untimely period.
Shanks has arrived, it’s therefore, too late to stand within the outside of the unprotected zone.
As Shanks confidently makes his way though the enemy ship to meet Whitebeard, a wake of newcomers are falling by him, due to his overwhelming Conqueror’s Haki.
What if these unfledged newcomers had stayed back as Marco had said? Marco is no fool, he’s a veteran, would make sense to assume had they promptly acted on his instructions, they’d still be standing, otherwise, why else would Marco propose they stay back?
We know the newcomers in Shank’s path were knocked out, however, there are other newcomers too. The other newcomers are the people all looking shocked and asking questions; they’ve never witnessed such a power before. Marco being a good leader reassures them to remain calm; the meeting of 2 Emperors is makes for a very volatile and tense environment as is evident.
Marco is also not telling Jozu or the other veterans to remain clam, they’re all familiar with Conqueror’s haki, unlike newcomers. Therefore, it can be inferred that there are newcomers scattered all over the ship; the newcomers who gout knocked out were just in the wrong place at the wrong time. Many of them are standing in the area that Marco pointed out as a safe zone which is why they’re still conscious.
Marco and Jozu?
Initially, we see Marco and Jozu at the bottom of the stair, it’s important to take note, that these stairs are by the Picket Fence which can only be found opposite the Ship’s entrance. It’s only because the entrance is a stretch of open floor space, that we find some Newcomers at the far widths of the ship.
As Shanks draws ever closer to Whitebeard, the Whitebeard Veterans and Newcomers edge back further away from the bottom of the stairs to just behind Picket Fence. Based on the layout, we can ascertain that Marco, Jozu and the Newcomers are all in the Safe Zone.
How Far was Shank’s Haki Spread?
If Shank’s Haki was spread throughout the entire ship, there would be no newcomers for Marco to tell to remain calm because they’d all certainly have lost consciousness if that were the case,this means it was only active to within a restricted area which was the route he took to get to Whitebeard.
And if one remembers, Shanks said he didn’t come to start a war, he was just ensuring his own safety being on an enemy ship and simply have a discussion with Whitebeard.
The point of this is to show that, the reason Marco and Jozu weren’t fazed by Shanks’s Conqueror’s Haki is because Shanks only restricted his Haki to within a certain area of the ship. The area Marco and Jozu were stood (including the newcomers beside them) was out of the range of Shanks’ Conqueror’s Haki. Were this not the case, the newcomers beside Jozu and Marco would have either fainted, while Jozu and Marco would have been intimidated; being that neither happened, it’s safe to say, Shanks’s Haki most definitely wasn’t extended to where they were.
*Theory by Hannibal Psyche