A scientifically motivated educated guess would be a possible combination of a few things. I reckon the comment about stressing has some stead, cannabinoids are battling for superiority over stress hormones and create less of an effect.
I've learned recently that it seems like the lungs do 99% of their absorption DURING the inhale only, while the lungs are expanding. I found this very interesting but haven't delved too deep into it. But shallow, less relaxed and quicker breathing would nullify the lungs' full ability for absorption even if the breath was held (seemingly rather pointlessly). I'm feeling that this is likely the main answer to this. The lungs are actually fairly useless at even absorbing oxygen considering that's their job. A very small percentage is utilised with each breath so they don't have a flying start anyway. Less available lung space will very quickly hinder their ability. A longer and deeper draw also means a hotter ember and more smoke flooding into the lungs. I believe long, relaxed draws without any need for holding your breath for more than a second will hit you more than a larger joint would if chugged down quickly without full lung expansion on each breath. Try and let me know if it works! Focus on long full breaths after each breath without holding. Keep inhaling until you reach the end of each breath after toking and think about your breathing for just one joint. I really feel like you should feel more smashed and less dizzy.