Right now, the rules state that if the announced prize at the beginning of a cash game is not won, then the game is lost. If you change this, then it opens up the possiblity of $8,000 Bag "wins" and $10,000 Rent "wins". The definition as stated is clear enough to allow for this not to happen because it is functional across all of the games.
The problem with your argument is that the victory conditions of It's In The Bag and Pay The Rent (as well as Gas Money, Fortune Hunter, and Grand Game) are based solely on price knowledge and, minus Fortune Hunter, a willingness to go all the way.
On the other hand, the victory conditions of Plinko (as well as Punch-A-Bunch, The Phone Home Game, and Half Off) involve price knowledge
and an element of luck; in the case of Plinko, landing all five chips in the center slot.
Given the very low probability of Plinko being won for its full stated value ($25,000/$50,000/$100,000/{foreign top prize}), some fans consider it won if the highest-value slot is hit at least once.
The rules are what they are. I'm not repeating them to force my "opinion" down people's throats; I'm repeating them because they're the damn rules. You can't just make them not be facts by declaring out of nowhere that they're opinions.
I am not saying you are wrong, Steve; I
do wish to point out that two of Roger's other rules (Half Off never uses Box 13 for the money, That's Too Much always has the solution in slots 3-8) have been broken by the current regime, so it does not surprise me that the Plinko rule would be as well.