Answer:
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.