Good reasoning but misapplied. I don't think the back door (2nd nut) flush possibility fully compnsates for the possibly tainted outs, and I count the backdoor straight as neglible on the flop because you have two internal holes to fill which is difficult, and in itself is a back risk-to-reward gambit. INO, there is a 17% chance the turn will give you an extra 4 outs on the river.