While the columns are artificial, they can be bet. Therefor they must be considered. What 2 in a row is concerned about is the fact that col 2 has 8 black and 4 red while col 3 has 8 red and 4 black. col 1 is equal 6 of each.
The question is can this be exploited. Obviously a bet on black and col 3 has an "extra" 8 posible red winners to help the col win. while red and col 2 gets an 'extra" 8 blacks. Is this an advantage ?
Basic maths says NO. the 2 bets are entirely separate, but it is awfully tempting to believe those "extra" reds and blacks might make a difference.