This is only true if you believe the people who used to be getting 3+ are now getting 0. This is unlikely to be the case because we don't see the number of people with exactly 2 partners going down.
If some of the 3+ people move to 2 and some of the 2s move to 1s or 0s, then you would see the same exact thing.
The data in the study you linked to its entirely consistent with what the OP suggested. We need to know what is happening at the tails to determine whether what you're claiming or what the OP is claiming is true. However, OP has a lot of anecdotal evidence in their favor. The study only provides data for the left tail of the distribution, but we need to see the right tail to know the full story. You could be right, but the OP's hypothesis is also supported by the data.
No that's not a possible explanation. Look at the charts for women. 80% of women have just a single partner in a given year and 60% have regular sex every week. This hasn't changed over time. For a hidden exponential right tail to explain this, you would need to believe that women are overwhelmingly switching into weekly, committed relationships with a small number of men and no others. You would also need to believe that these alpha males are bedding all of those women weekly. That doesn't make logistical sense, and isn't the story people are trying to tell either (that a small number of men are doing a different woman every other day and keeping them satisfied and off the market).
These alpha male type men may exist, but they're a drop in the bucket compared to well documented factors like worsening economic conditions.
