Do even the least bit of reading about lung physiology and function, and you'll see that the gas exchange and/or absorption of anything you breathe in occurs instantly. It literally occurs with the initial expansion of those little alveoli, the tiny air sacs where the chemical exchange occurs. Holding a hit doesn't do anything to make you higher, just like holding a breath doesn't do anything to make you absorb more oxygen from the air you breathe. In fact, holding a breath or hit likely hinders further absorption because it postpones the exhalation of the carbon dioxide and, in the case of cannabis smoke, other smoky by-products, which completes the emptying of the lungs and gets them ready to take another breath/drag.

If anyone can find anything saying otherwise, it'll be written by someone who knows nothing about the physiology of inspiration/expiration and will be completely bogus. The chemical intake occurs immediately. Holding hits just gives your lungs longer contact with the bad stuff, not the good.
The problem with this website is that people claim to "know" about things. Are you a doctor specialized in lungs? if no and even if you are what the heck do you know? "Gives your longs longer contact with the bad stuff, not the good?" seriously how can you say this with a straight face