The TouringPlans.com Crowd Calendars are based on statistical analyses of millions of historical wait time values. We use that process to predict wait times for future dates, and our Crowd Levels are based on those wait times forecasts.
We do not know how other operations come up with their predictions, and we have no expectation that any other efforts would be similar to ours. An analogy might be that even knowledgeable people might come up with different looking NCAA Basketball Tournament brackets: even if there are some common picks, no one expects all details to be the same since people use different methodologies.
We've been at this a long time, and we share information about our predictions and the "observed" levels for the parks. We do a good job, but predicting wait times has a fair amount of uncertainty: weather, unexpected breakdowns, and attendance surprises can all impact how well we do. Aware of this, we constantly evaluate our performance and make adjustments in response to trends that we detect in the parks.