Absolutely, I find that I'm naturally on the inattentive side but hyperactive symptoms present when I'm forcing myself to pay attention to something (like a lecture) and not let my mind wander.
Just a quick question (in relation to my comment to your other comment): In these lectures that you find hard to concentrate on: Could you say that you feel disgust/repulsion? There doesn't need to be a rational reason, disgust is completely trained and can be felt for anything from the look of the windows to the hairstyle of the lecturer to the actual topic.
If so, then your inattentiveness could be your mind trying to escape that feeling.
That's the worst part, I don't even know have a guess as to why my brain wanders off. It's just gone and I suddenly realize I haven't been paying attention for 10 minutes. I don't think disgust/escapism can explain it, because it can be an extremely fascinating lecture. But my mind will grab on to a topic and continue on "cruise control" internally before realizing the road has a curve in it. If I had to pick something, it would be related to hyperfocus that just gets triggered off of a random thought.
Not meaning to get too personal here, so feel free to ignore this, but it still could be that you're zoning out to avoid some negative emotions.
Could it be that you're dreading something that is "implied" by the lecture in a way? Maybe the practise that you feel obliged to do? Maybe the impact the lecture could have on your work or schedule? Maybe just the end of the lecture and back to whatever comes after?