Universe 6' structure conditions are similar to Universe conditions. Species are same, races are same, planets are same, even planets names are same. But only time is different. Universe 6 is somehow ahead of Universe 7 in terms of Time .
Here are some proofs for this theory.
1) Universe 6's Earth was destroyed and all humans were extinct due to a stupid war.
2) Universe 6 Saiyans has evolved to that time, where they don't have tails with them.
3) Even the name of vegeta's attack GALLIC GUN is same in Universe 6.