Ok, so database search does seem to work for me at least. I found a 2020 Kissinger cancellation but not the 2018 one. I am curious about its absence. There was only one NYU issue recorded that year. Looks like you might have found a missing data point.
Anyway, if they stick with the current methodology until 2030, I’ll say that’s a solid start. That’s 15 years since 2015, which is a reasonable arbitrary year past which the effects of modern social media would be in play. Trends should be very clear at that point, and data collection methods shouldn’t be too different from the start of that period.
As for why I respect their reporting, I read some about their methodology in the past, when I first started following them, and I also have read criticism of them, which I did not find compelling. I don’t generally dig into every little detail of it because I have trusted sources who trust them, and that’s how you generally find your way in a world with too much data and too little time. Regardless, although they are imperfect (that missing data point!), they seem to be mostly thorough, and reading through the methodology PDF it looks like a good overall approach.