Late to the discussion, but cancellation/hedging definitely is a thing.
The crux of the thing is variance... whoever is the underdog wants to maximize variance, and whoever is the favorite wants to minimize variance.
So if you've got two WRs that have roughly the same projection, but one is a Crowder type with a high floor and low ceiling, and the other is a Marvin Jones type with low floor, high ceiling, which one you should put in your lineup depends on whether you want to increase or decrease variance that week.
Cancelling out the other guy's QB by starting one of his WRs is another way to decrease variance, so it makes sense to do it if you think you're the favorite that week.
This theory is all built into the algorithms FBG uses in the myFBG app. There's documentation on it somewhere.