Just one problem: he has it wrong on the first song. He says D minor, when it actually switches between G Dorian and Bb major (technically, Bb Lydian). His D is the fifth of G minor/Dorian, and the fifth is frequently used as a drone note because it fits with both the I and V chord (the tonic only fits with the I, IV and VI chords)—also, the fifth fits the III chord, which is prominent in this song. He's right that the note you intuitively pick is likely to be the first (tonic), third or fifth of the key, but that still leaves you with four choices and the mode to determine. Why four? Because the third could be either major (four semitones above the tonic) or minor (three semitones above the tonic), depending on the mode of the piece.
The scale as I hear it runs G A Bb C D E F G: G Dorian. (Dorian mode is like minor mode except that the sixth note is a half step higher, as in a major scale.) This same set of notes matches Bb Lydian and D minor (relative modes). So it's not surprising that he fixes on D minor as the key, as it's familiar to his limited way of viewing keys (they're just major or minor—or blues—right? Wrong.)
The piece begins on the tonic chord, G minor, and the chord sequence, repeated over and over and clearly heard in the bass, has the following roots: G Bb D C Bb—I III V IV III in G minor, with the first three tracing the G minor chord. The singer and accompaniment begin with a very clear G minor chord—she starts on the root and drops to the fifth. In fact, throughout, she's basically singing notes in the Gm7 chord—remember, this is trance music, which tends to be minimalistic. And although she does end on a D, the chord underneath her is Bb (major), of which D is the third. Given how protracted this chord is, there's a tonality change here to Bb major (technically Lydian)—songs often do this kind of tonality shift between relative modes, and it can be hard to pinpoint just where the shift occurs because the piece usually sticks with the same set of notes and same set of chords in common. In fact, you could view the entire progression from the standpoint of Bb Lydian: IV I III II I. But I think it's more correct to view this as a modally ambiguous song that flips tonality between the two relative modes. What is pretty clear, however, is that the tonality (key) is not D minor, even if the scale pitches happen to conform to D minor, too.
He's also wrong about 90% of (modern) songs being in minor mode. Major mode (and its close variant, Mixolydian mode) dominate most pop music. Lydian isn't a common mode, but Dorian is used more frequently than people realize. Minor mode may dominate the genres of music he listens to, but that's another story.
