In a lot of countries, drinking wine is fine (as in legal) at ANY age.
It's the purchase that is so often regulated.
(And you're right, in many places the latter limit is lower than 18. For example in Germany, Austria, Switzerland, Denmark and Belgium, non-spirits like wine and beer can be bought from 16.)
The two (drinking age vs. alcohol buying age) often get confused, but consumption limits per se are actually pretty rare. (Assuming it takes place in private – laws regarding drinking in public are somewhat more common.)
Maybe he's thinking about the story about how Queen Victoria used to find the claret at state dinners too weak for her, so would take a flask of Royal Lochnagar whisky to supercharge her wine.[1]
