If it's a major scale, you're not supposed to play minor third. Besides "every third note" will eventually be every note because there are 7 notes in a major scale. So, by the second octave major second will be one of the "fizz" notes (similar to ninth chord, stacked 4 thirds, having a major second).

This can be a legit exam BTW, some contemporary Western classical styles use these kind of patterns to make music.

E->G is a minor third.

Is this really relevant? I'm not understanding why it would be. I was referring to Eb (minor third of C) and E (major third of C).

Huh? He’s not talking about creative choices, dude. The third note of a major scale is objectively the major third.

The third note of a major a scale is also the sixth.