I've actually attended three different Division and Corps level wargame exercises, and saw a lot of things that stuck with me within them. One essential thing to remember is that they aren't intended for anybody to win or lose, they are intended to learn how a specific scenario may develop. That is the intent of them. However, people too often get the mindset that they MUST win. Both because it's human nature, but they also understand that it can affect the career of a high ranking officer. Gamesmanship creeps in. I remember a documentary somewhere about a live troop exercise in Hawaii regarding amphibious landings. The attacking commander arranged for delivery of porta-potties in a fake area as part of his deception plan. Effective for the game, but not something that would happen in real life.
But remember, that nothing EVER happens in a vacuum. A wargame simulates a specific point in time. However the years, months and days leading up to the events within that wargame are not inconsequential. You spend that time learning about your enemy. His equipment, his tactics, his abilities. There's a reason that scripting is done in these scenarios, because your enemy is who he is. He's not going to do something for 20 years, then suddenly be 100% different for that specific battle. Sure, he may pull some surprises, but that base capability is still going to have some influence in his actions and abilities. From what I've seen of this exercise Van Riper ignored the script, and claimed that he was 'constrained' by that script. It's not supposed to be rules of the game, it's supposed to simulate the rules of history, and it's supposed to be a backstory of who the combatant is. From my experiencs, the opfor generally follow the general practice of Soviet, North Korean or other armies that have a high potential of being enemy forces in the near future. This is in organization, equipment or tactics.
As to his claims that he was forced to do things in order to ensure a US "victory". He's probably both correct, and full of absolute crap, at the same time. He probably was directed to allow certain things to happen, no doubt about it. Not to ensure a US victory though, but instead to allow the scenario to progress. This goes back to what these war games really are, which is a learning exercise, as opposed to what they are not, which is a contest to win or lose. If you are simulating an amphibious landing, and the enemy sinks all your ships.... you learn from that. But that enemy probably has some interesting concepts for the continuing land battle should the beachhead be established. At least he should have a proper plan depth in that regard. So you need to progress the scenario to that point, and ensure that you have it progress through every phase of the battle. Simulate the full battle, not just early phases and call it a day.
Then, after the actual wargame, you spend a huge amount of time evaluating what happened. You pick it apart, piece by piece, and evaluate the effectiveness of the tactics on both sides. So I tell you right now, there was probably a lot of discussion on Van Ripers tactics. His concepts have some validity to them, but again... NOTHING happens in a vacuum. If you're going to use 500 fishing boats with surface to surface launchers on them, they're going to be in a harbor somewhere, and that is a very very yummy target for a 688I tomahawk strike with bomblet warheads.