Looking through it now, I believe the conversation I was in was referencing this: www.nature.com/articles/npp2014236 , specifically because it’s not a random group of scans. It’s a rather ambitious study, from 1989, and is, as it was told to me, where the journos got ahold of the “25” number. In fact, the first article you link’s sources seem to all have the 1999 version as their first reference, probably because they’re all pre-2014. No mention of money in the paper, obviously, but it does talk of the study as “ongoing”, and I couldn’t find a newer followup, so, uh, yeah.
As I was digging, though, I ran into this: www.nature.com/articles/s41467-023-42540-8 , so the number you go with, if it even makes sense to go with a number, is still a matter of what you want to measure, I’d say.