It seems that more high quality data are needed. But it is worth noting that of the 3 points and 1 upper limit with diameters below 1 km, none have ages exceeding 10 million years, whereas the average age of all craters is around 100 million years. So this is suggestive. I would have generally expected small craters to be young and big craters to be old. Hence the only small craters around would be young ones.
Big craters come from impacts with big objects.
Since these are rare events, I would not expect them to happen very often, and hence the typical big crater should have an old age. This plausibility argument does not seem to be convincingly borne out in the analysis of part 1. But there may be biases in the selection of craters used in the table that prevent us from drawing the correct conclusion. For example, it would be nice to have more points for craters of less than 1 km diameter. And perhaps bigger craters are really older, but it is just more difficult to identify craters exceeding 100 km in size.