In the last episode of season 3 of The Man in the High Castle we are told that individuals can only travel to an alternate reality if
their alternate self had already died in the alternate reality.
This explanation is given for why
only one out of the four test subjects survived the Nazi experiment to travel to alternate realities -- the survivor, just an "ordinary" girl, was apparently the only one whose alternate self had already died in the alternate reality.
This explanation does seem to make sense as a way to avoid
the possibility of an individual meeting an alternate version of himself from another reality.
The explanation also conforms to what we know about almost all the other characters that travel between realities:
1. Trudy was killed in the reality in which the Axis won so her alternate self from "our" reality (in which the Allies won World War II) can travel to the Axis-conquered reality.
2. The alternate Trudy who traveled to the Axis-conquered reality tells us that Juliana was killed in her reality, so Juliana can travel from the Axis-conquered reality to that reality.
3. The dark-skinned woman Mengele was performing skin-pigmentation experiments on was killed an experiment gone wrong so her alternate self was able to travel to the Axis-controlled reality, where she too was captured and experimented on by Mengele.
3. Tagomi's assistant, Kotomichi, was injured in our reality by an atomic bomb and managed to travel to the Axis-controlled reality while meditating to endure the pain from his wounds. We don't see an alternate Kotomichi from the Axis-controlled reality so Kotomichi's case at least does not contradict the explanation that you can only travel to an alternate reality in which your alternate already died (presumably the original Kotomichi from the Axis-controlled reality was killed earlier, perhaps during World War II).
However, Tagomi's case seems to contradict the explanation. In season 2 we saw Tagomi visit our reality, where he is seen and recognized by his wife and son. Tagomi from our reality is estranged from his wife and son but Tagomi's family
clearly think he's alive (they don't act like they've seen a ghost) so apparently Tagomi's alternate self is still alive in our reality and the Tagomi from the Axis-controlled reality shouldn't have been able to travel to our reality.
It has been awhile since I watched season 2 so perhaps I forgot something about Tagomi that wouldn't contradict the explanation given in the season 3 finale. I found a recap of one of the season 2 episodes in which Tagomi traveled to our reality which confirmed what I remembered but doesn't mention anything that would explain how Tagomi's case doesn't contradict the restriction on "travelers".
How was Tagomi from the Axis-controlled reality able to travel to our reality? Was there an indication in the show that
Tagomi from our reality had died just before Tagomi from the Axis-controlled reality traveled to our reality, and Tagomi's family in our reality hadn't learned of his death yet?
Is there some other explanation that doesn't contradict what we were told in the season 3 finale?