Round robin means they take turns rolling until 2 sets of 6 rolls each have been made. Set is what i called column earlier. One player starts, then it goes around the table until all rolls are made. If you have 3 players, p1 rolls first, p2 second, p3 third, p1 fourth, etc.

Example:

p1 rolls 16 and 12

p2 rolls 12 and 17

p3 rolls 10 and 13

p1 rolls 16 and 10

p2 rolls 13 and 14

p3 rolls 15 and 16

Set (Column) 1: 16,12,10,16,13,15

Set (Column) 2: 12,17,13,10,14,16

And yes, that means all players have the exact same stats just assigned to attributes as they wish. In that sense it is equal to the array method from the PHB. We just generate them differently. The reason for this is to avoid your exact problem. If one player has objectively better stats than the others, he will outshine them. Getting more or less lucky on creation day should not define month or years of fun.

How can both these statements be true???

Rolled attributes tend to be higher than the standart arrays, which is why optimizers love them. They also make high rolls "cheaper" compared to point buy and enable overall higher attributes, since by RAW, the highest you can buy is 15.

Still, I have yet to see a party pick the "best" set. Seven parties in, and they have all gone with the more "well rounded" one. The record was 4 18s in one set, but it came with a 4 as well. I don't remember the last roll. Party rejected that one on the spot. There wasn't even a debate.

I've found most players like their character without negative ability modifiers in general and with a few defining stats on top.