In Universe 6, this version of Gokū was forced to bear witness to the deaths of his son and friends when they failed to defend the planet from Bojack and his thugs. Being already dead, Gokū was not allowed to abandon his post and did not intervene in the battle to assist Gohan (unlike in U4, 16, 18, and 20), respecting King Kai's orders. This did not slow Gokū down from visiting them in King Yemma's palace, making everyone surprised to see him so abruptly. Gokū requested an opportunity from King Yemma to return them all to Earth in order to face Bojack once more, but he was turned down instantly.
King Yemma decreed that Bojack was not the same kind of threat that Cell was and did not seek universal destruction; determining that the Z-Fighter's wish to go back was a selfish one, making them ineligible to be granted a second chance.