There's zero basis for assuming any of that. The most likely situation is a power law curve where the vast majority of users don't use it much at all and the top 10% of users account for 90% of the usage.
It is very likely that you are in the top 10% of users.
True. the article also has zero basis in its estimating the average usage from each tier's user base.
I somewhat doubt my usage is so close to the edge of the curve since I don't even pay for any plan. It could be that I'm very frugal with money and fat on consumption while most are more balanced, but 1M token per day in any case sounds slim for any user who pays for the service.