No, we just had to match or beat Sussex's bonus points, which we did. The gamble against Yorks would've definitely been appropriate if we'd needed 2 wins, but clearly we didn't. Moreover a loss was worse than a draw, as we are now seeing. I think it all comes down to whether Yorks had a good chance of making the runs, or if we had a better chance of bowling them out. If the former it was a bad gamble, if the latter a good one. Bearing in mind Yorks are one of the best domestic teams ever I don't think it was a wise gamble, but clearly many disagree.
Anyway, the real screw up was the first innings against Somerset. If we'd got 4 more batting points there then Sussex would need to win tomorrow (assuming we do beat Notts), regardless of the Yorks defeat.