There is no contradiction between those sentences. The Gulf Stream contributes to those differences, but is not the only cause.
Incidentally the basic explanation is obvious if you know something about climate. The powerful upper air current in question is certainly the jet stream, which at that latitude blows from west to east, and carries weather patterns with it. (The source of the jet stream is a Hadley cell.) The result is that Labrador gets weather off of land, while Europe gets weather off of the ocean. If you look at pictures from space, oceans are darker than land, and therefore absorb heat better. (This is doubly true in winter!) Thus the surface of the ocean tends to be warmer on average than land. (As well, water holds heat better, and so tends to fluctuate less. This leads to milder winters and summers.)
The moral? The fact that someone doesn't try to explain something doesn't mean that they don't understand it.
Incidentally the basic explanation is obvious if you know something about climate. The powerful upper air current in question is certainly the jet stream, which at that latitude blows from west to east, and carries weather patterns with it. (The source of the jet stream is a Hadley cell.) The result is that Labrador gets weather off of land, while Europe gets weather off of the ocean. If you look at pictures from space, oceans are darker than land, and therefore absorb heat better. (This is doubly true in winter!) Thus the surface of the ocean tends to be warmer on average than land. (As well, water holds heat better, and so tends to fluctuate less. This leads to milder winters and summers.)
The moral? The fact that someone doesn't try to explain something doesn't mean that they don't understand it.