Adiet high in saturated fats increases a person’s risk of developing heart disease. regular consumption of red wine reduces that risk. per-capita consumption of saturated fats is currently about the same in france as in the united states, but there is less heart disease there than in the united states because consumption of red wine is higher in france. the difference in regular red-wine consumption has been narrowing, but no similar convergence in heart-disease rates has occurred.

The reduction   of the regular wine consumption(as implied in the question) among the young adults in France is responsible for narrowing of red wine consumption gap between the two countries. Generally, heart disease do not manifests until later age of 65 and above in human, therefore this explains the reason why the rate of convergence is not decreasing despite gaps in consumption.

Manifestation of the heart diseases will not  be  diagnosed until the later  age, therefore when they are young, and not consuming wine,  heart diseases will not occur and no similar convergence  in rate  was noticed.

Besides some young adults may not reach this age  of heart disease prone, thus  diagnosis may not be available for data documentation.