Hey Kyle,
There is a similar question asked in the past on here if you want to check it out in regards to projects endpoint.
The short answer is that updatedAt in the forecasts endpoint would only be changed if you changed the name of the forecast or added/removed tags.
We don’t update the updatedAt date-time if the forecast runs or if you modify the parameters, etc. We also don’t modify updatedAt if you convert the forecast.
The best way for you to ensure that the forecast has been modified from the forecasts endpoint would be to check the rundate, which is updated when the forecast is run.