There are many that have seen Bash play
When Slav played a 4, Egan wasn't going to be displaced and most managers in Pro football don't play a right footer on the left.
I think in an ideal world you would be correct but I can't think of many pairings where we've genuinely had a proper mix.
From memory and not a definite list:
Stancliffe and Smith - both right footed.
Stancliffe and Thompson - both right footed.
Stancliffe and Hill - both right footed.
Stancliffe and Morris - both right footed.
Gayle and Morris - both right footed.
Gayle and Beesley - one right, one left footed.
Page and Morgan - both right footed.
Page and Jagielka - both right footed.
Morgan and Bromby - both right footed.
Morgan and Davis - both right footed.
Morgan and Jagielka - both right footed.
Morgan and Kilgallon - one right, one left footed.
Maguire and Collins - both right footed.
Collins and Butler - both right footed.
Then came Wilder with O'Connell signing early.
So I'd tend to agree it is better but probably driven by statistics of the population; only one in ten is left handed, then it isn't possible.