Since Deryl started messing with it, I have an inkling that it may become a later plot point. However thinking about it in a broader sense, WW has introduced so many monster-related technological concepts through the memory flashbacks to sea/sky humans, that the serum looks like nothing and frankly I don't think that that reaching level 5 is anywhere close to the end game.
The vestige had intimate knowledge of ascension concepts, things that not even the level 5s of current humanity are aware of, and their progress had been ultra slow, depending on Henri who lacked the fine control to explore them. This is an indication that the althumans in general had achieved level 5 on a great scale.
If Henri had the Lie trait, he would probably had a much easier time navigating the dreamworld, which is sustained by Lie. He seems like he has the Truth trait based on how his power manifests, but I just can't observe the Lie in any shape or form.
I disagree with this, the Althumans were certainly more advanced at large in a ton of aspects, both in 'base' technology(Aquatic and Flying Cities) and on Monster-related Tech, with things like the Gun MC and Michael found, still, I think the perfect serum of Xanthe is something special, as he himself seem like an oddity on intellect/creativity or whatever allowed the creation of the Evolution Serum, why I think this?, for two reasons mainly, the Sky People had just some wack-ass liquid that allow partial transformation on Monsters, the wakeblood, something that Xanthe created(and gifted to Klaus) but regarded as a failure, and point two, Aos was an elite Soldier as a Spawn, and upon becoming a Monster, he killed a bunch of Higher-ups, the issue is that Aos himself at that moment was *just* an A-Rank monster, Trio of HERO aside, the Captains or lieutenants would genuinely stomp any A-Class, so I don't really think the Final Evolution was something common on that iteration of Humanity, or even in general, as Being Completed(level 5) seem to be regarded by Monsters as something unique, even the Eye mention it as something notable when seeing the fight between Nico and Ella during the BoD DeadEnd.
As Henri being Paradox or not, there is nothing official yet, he can be whatever Deity, but I think Paradox is by far the most likely, him having troubles exploring the Dreamworld would have less to do with the nature of his powers, and more with Henri himself being far too mentally unstable and not embracing nor having control of his powers, is something mentioned on the game, both by Lisa and seen in how Xanthe/Dexter pretty much had Henri in quarantine during who knows how many decades.
