@kaialone replied to your post:
I kinda just imagine that they initially *weren't* chosen and came to the Digital World by accident. Their status as "chosen" developed over the course of their adventures in the Digital World. But this is not explained as such to the Adventure kids in order to keep it simple for them. (<- Yeah, I realize this still qualifies as a retcon.)
This works too! This is basically along the lines of what I've been calling "the Oikawa loophole" (in that Oikawa’s presence establishes it’s possible to be “a human who bonds with a Digimon but is not recognized as a Chosen before 1995, then is retroactively recognized as one afterwards”), and I’ve personally used this to explain how Wallace met his partners before 1995.
According to Homeostasis’s testimony in Adventure episode 45, the significance of the Hikarigaoka incident to them and the Agents in 1995 was that it made them realize that a Digimon bonding with a human allows for evolving spontaneously (instead of “naturally” over a long period of time like most Digimon in the Digital World). So under this idea, I would imagine Himekawa and Nishijima and the others fell into the Digital World by accident in the eighties and bonded with their future partners, but Homeostasis and the Agents weren’t sure how the kids and Digimon pulled off what they did at the time. Then the Hikarigaoka incident happened, which confirmed “okay, it’s definitely the human contact that did it,” so they scanned the data of the local kids and the rest was history, and Himekawa and Nishijima were retroactively considered Chosen Children later.
This does mean going against the novel, but not only is that more than fair game because the novel is already canonical AU (in a sense), the reason I bring this up is that this novel is where we got the name “Homeostasis” from in the first place. In Adventure proper, the entity that spoke to the kids in Adventure episode 45 was only named “the one who wishes for stability”. So if you want to go hard-in on disregarding the novel, it’s also entirely possible to say that “the one who wishes for stability” in Adventure episode 45 and “Homeostasis” in tri. aren’t even the same entity to begin with, which opens even more possibilities. (As you say, this is an obvious rule patch, but it’s fun to play with this kind of thing.)
Sorry, I hope I wasn’t too nosy/intrusive or putting you on the spot, I just thought it’d be interesting to expand it a bit further!