Axually, it’s just the opposite. And here’s why.
In a single-QB league, your Mahomes or Dak gives you a huge advantage, because they will score 6-7 more points per week than most other QBs. In a 2 QB league, your QB score is no longer dependent on just one guy, but an average across TWO QBs. Having Mahomes and Darnold is functionally equivalent to having Cousins and Ryan.
Sure, if you can get Mahomes AND Dak, you’ll enjoy a positional advantage at QB, but the draft capital you’d have to expend to get 2 of the top 5 QBs in the NFL would leave the rest of your team pretty hamstrung. I would guess you’ll lose a lot of the 10-12 point per week advantage you gained at QB by having subpar RBs and WRs.
So really it’s better to run around scooping up the falling studs than try to compete with the alpha stooges killing themselves to get QBs in that Superflex/2QB draft.
And what’s wrong with starting the QB6?