Let’s call this an example of metaphoric subtext. It’s very similar to the third-person subtext used in Love Jones, but this is even more blatant. This scene in Sideways is also a much-noted example of subtext, but it’s worth presenting again as its overtness makes it a great teaching scene. 

In the scene, two wine enthusiasts talk about their passion for the beverage, but the wine becomes a conduit through which they actually talk about themselves.