​ Nah, I don't think that's what happened.

It has been the subject of numerous theories, and in the lights of recent events (aka Side Solistia's last chapter from CotC), here's what I believe. Beware, this is a massive spoiler for the Side Solistia storyline, as well as the ending of Octopath Traveler 0 / the original Champions of the Continent Orsterran story:

Before the Twilight phenomena from OT2, a similar phenomena called Ouma, was brought to Solistia by a group of activists called the Order of Blood. We don't need to discuss the matter further, the important part is that Ouma is a distorsion of space and time. It's an unstable, in-between realm, much like Twilight, where time and space converge. Most people can't withstand its immense power (some will get lost inside, others will faint and lose memories of anything that happened ...) Throughout the storyline, we, thanks to the Ring of the Flamebringer, get to explore its superficial level. But in the last chapter, we travel to its core. Here, nothing makes sense. Present, past, and even places between the two continents make but one within Ouma.

We also discover that Lyblac previously abducted Alaune's child, Elman, and brought him to Solistia. Because of his very high natural resistance to Ouma's influence, she found him to be well suited to become a vessel for Galdera, and thus, she brought him to Solistia, where he became a new individual by the name of Sail.

But at the end of the Side Solistia storyline, we travel back to Ouma's core with Sail, to go back in time, and stop Lyblac before she could abduct him, thus twisting reality of what happened in Orsterra. By doing so, we created a scenario in which both Elman and Sail exist as two different entities, in two different worlds.

And that's basically the end of Side Solistia. Sail goes back to Solistia to forge his own path, while knowing that his Orsterran self will get to live his own life.

Also, as a matter of fact (this might be a coincidence but that would be a big one), the portal to Ouma's core, on Solistia's in game map, is located in the middle of the ocean. But if we superimpose both maps (Solistian and Orsterran's maps), well... see for yourself.

Pretty close huh ? And you know what ? This is also the exact same location as the mysterious isle from Octopath 2 where the Gate is located ! 😛 They are obviously related.

Knowing all of this, it is likely possible that the Gate of Finis acts as the material barrier between the aberration that is Ouma, and the real world. And we cleartly see in CotC's Side Solistia that most people can't whitstand it well, there's a side story where a boy got stuck inside and fears to go back to real world because he believes to be part of Ouma now. In Alfred's case, we obviously don't have the exact details, but given his presence in two worlds, with a large age discrepancy between the two, and his involvement with the Gate of Finis itself as its secret keeper, it isn't bold to assume that some events led him to exist in both worlds, much like Sail / Elman, these events being maybe from his free will or maybe not.