I will still use EQ when and where appropriate, but I don’t think I used any during the recording of those studies. I wish I had taken notes during the recording several months ago as I am having a hard time remembering the exact setup. But I do remember my general approach was to use minimum processing (delay pedal, and maybe very mild compression), a clean sound system, and so I could explore technique only as a means to achieve a wide range of sounds/noises/timbre.
So in practice, I would say I will use EQ for effect and to fit the space I am playing in. For example, the blues melodica/guitar track was recorded outside with my blues setup that includes the Vox AC10 guitar amp, which has bass and treble tone controls that I change considerably based on the song and the melodica I am playing.
I guess my advice would be, by all means, use EQ. But use it only after you tried other means (melodica selection, amp selection, microphone selection, effects selection, and playing technique) to achieve the sound you want.