The studio and the news are not going to confirm every small detail, and the wikia is here for all of those details to be added. They are going to have to be found by people playing the game or watching videos of other people playing the game, otherwise this wikia will never be more than an echo of the official site. They won't give information about canceled products either. This wikia can be much more than that! But if needs you to risk some bad information for the much bigger benefit of growing this awesome wikia. So I think the conclusion here is that walktroughs are a useful source of reliable information.
One thing to consider: would most pages have spoilers? if so, then per-article notices would quickly become over-done, and the main page notice is better. But if they are being used relatively sparingly, they work well. "Experience" isn't preserved whether you exposed to it the first, second, third, or fourth time and so on. If it's not so good the second time then the first then it's maybe not so good at all. If you're interested in certain information then it's inevitable you will be exposed to it. It's better to be sooner than later and get it over with. It doesn't "help the game along" as games don't get worse over time. Only your expectations change. A game from 1999 is going to play the same in 2017. Not giving information until at a certain point of time makes earlier actions hypocritical. And if the product is canceled and you report on it that the owners of the canceled product didn't give any information and you still think you're in the right then it's time to take a hard look in the mirror. "Spoilers" don't affect anything. Games are still re-released regardless and DVDs of movies are still released despite showing movies in theater.
Point of view and objectively a nonsense. This wiki functions as a community, some decisions have been chosen and of course you did not read them. The wiki grows progressively in time and there is no urgency to have an exhaustive database as soon as possible. You did the same thing with Lao or Elma real appearance, that you came on the wiki after a long inactivity just to publish massive spoilers concerning the plot revealed at the end of the game, while the game was not or had been just released out of Japan. Moreover officially XC2 is not released yet, that is again a bad intention toward the community.