Why did Trunks travel to Age 779 in DBS?
In the 4th Timeline (the timeline Trunks created ), the U6 Tournament took place in
Age 779 and Super Shenron was summoned right after. The Super Dragon Balls would be inactive for 1 year before they could be used again. Because of this, Zamasu used the Time Ring to travel 1 year into the future (to
Age 780) and swap bodies with Goku. He would then flee to the 3rd Timeline and start Zero Mortals Plan there.
Trunks would be heavily outmatched by Goku Black so he would use the Time Machine to get help in the past he helped save many years ago (the main timeline we follow). Now here's my question: shouldn't Trunks have gone to Age 780 instead of Age 779? Shouldn't he have arrived in the world where Goku, Chi-Chi and Goten were killed by Black?
By going to Age 779, Trunks essentially created a brand new timeline, something that he was against unless absolutely necessary. Am i missing something here? Was this ever explained?