So, let's walk through this as Naruto Uzumaki, loyal Leaf-nin who wants to believe us but still doubts the seance because for all he knows we heard about the Toad Thrust and forgot about it.
Hazou claims that the O'Uzu rift leads to the Pure Lands. You've read the report and would like it to be true, but you aren't convinced and need more proof before you believe. You know or at least strongly suspect that Asuma's in the same boat of waiting for more evidence.
Hazou says that he can open the rift, and he needs your help. You go along with this because you want it to be true. You see the scenery on the other side like he said, but that wasn't the part you were doubting. Until Hazou finds someone to rez, your priors haven't shifted. Maybe you ask him to go looking for someone as proof of concept, but maybe not. After all, this is the research trip so that they can better equip themselves for a real expedition, and the threat of Akatsuki looms over this location while there's no guarantee anyone is nearby the rift site on the other side (if it even is the afterlife in the first place). You relay all this to Asuma but this doesn't shift his priors for the same reasons it didn't shift yours.
Hazou's ready to go for a proper expedition. In this hypothetical we couldn't move the rift so we're trying stealth necromancy instead. You open the rift and Hazou walks in, and you close the rift behind him. You'll have your answers when you go back to re-open the rift, but for now you still know nothing that you didn't already know. You relay this to Asuma, the two of you both privately hope that Hazou's right and your respective loved ones can be saved, but epistemically your stance still hasn't changed: wait and see, proof will either come or it won't.
This is stealth necromancy, so Kagome goes back to exfiltrate Hazou without Naruto present. Naruto, and thus Asuma, is still under the impression that Hazou is still exploring the other side of the rift. Kagome exfiltrates Hazou and whoever Hazou found, any and all options that we've obtained from finding and rezzing people have been actualized. Maybe we found Jiraiya and he's ready to march back into Leaf and take the Hat from Asuma. Maybe we found Pein and successfully convinced him to owe us a life-debt and enshrine Uplift in the new world order. Whatever the gains, we have them now, and Naruto is none the wiser.
But maybe stealth necromancy hits a snag, and Kagome can't sync up with Hazou to exfiltrate him. Worrying for Hazou's safety, Kagome returns to Leaf and brings Naruto to the rift, just as Naruto expected would happen since he had no clue stealth necromancy was even an option. Naruto opens the rift again and Kagome et al. goes in, and hopefully Hazou's safe enough to exfiltrate. Whoever Hazou found is now known to Naruto, as well as the fact that this is truly the afterlife. Only in this scenario does Naruto run back to Leaf and tell Asuma to secure the O'Uzu site as soon as possible.
At the end of the day, the only thing that constitutes meaningful information to Naruto is the actual resurrecting of someone. Everything else is stuff he has no reason to disbelieve, which already proved insufficient to fully convince him. We will have, at the very minimum, until Hazou first escapes the Pure Lands before Naruto truly believes, and if we play our cards right we may have even more time than that.
I note, for instance, that even if we move the rift and remove the Akatsuki OPSEC problem we would still need Naruto's help opening it, and would thus similarly wind up exiting the rift under the watchful gaze of an unquestionably loyal Leaf-nin. (While we would not need to let the rift close again if it is in a safe location, by the same token we do not need to leave the scene quickly to avoid Akatsuki attention, and consequently Naruto is far more likely to stay there and wait through the preliminary exploration until we have proof of concept). That is to say, Naruto running back to Asuma as soon as we rez our first person isn't an unusual fail state of stealth necromancy, it is the expected outcome unless we have some way to circumvent him.
Incidentally, it's not implausible that Primordial Sealing will allow us to circumvent Naruto entirely. If it can channel vaster amounts of ambient chakra than the paper Minato seals can, it's not implausible that it will work as a serviceable substitute for Naruto's bijuu power. If this proves true, not only stealth necromancy but Plan A "move the rift" necromancy becomes much easier for us. But the core of stealth necromancy is that even without this innovation we do not necessarily need Naruto for our exfiltration, which means we can buy precious time and initiative by having only Team Uplift standing outside the rift as it opens. No Leaf, no Akatsuki, nobody even suspecting a thing, and all without needing to move the rift in the first place. I'd say it's a perfectly serviceable Plan B.
