More than one of them showed up over there and claimed that they were also dead. According to that other trainer Eliza, though, they can just come back in new bodies. And seeing how they apparently have a direct path from there to here, it appears they were stretching the truth.

...one of them tried to make a deal with Akko. Jun and Eliza were...extremely aggressive in dissuading that. Eliza actually kicked the first one we saw into the void somewhere. [God, that girl definitely has anger issues. One reason he's been keeping his distance from her despite them having Pokemon training in common.]