The tweet was saying instead of take the cash out, to make hedge bets against Diggs. The screenshots show the math better. It makes sense and isnt wrong it just assumes you have 5k in your account to hedge with. In this scenario, if you did, you could guarantee a payout higher than the cash out I believe.
But yes, Diggs didn’t get over 50 yards and that parlay failed. So if he didn’t hedge or cash out then the bettor got nothing, which means he should have cashed out. If he did have the hedge money then yeah, make the bet.