That's simply untrue.
You get "higher" from 1g of cannabis cooked into food for a host of reasons, that have nothing to do with CBD.
When you smoke, you might capture %20 of the cannabinoids, of which only a fraction is in the decarboxylated THC form, the rest is in its innactive THCA form. When you cook food with cannabis, especially baked foods where the products are more evenly heated over time, the majority of the THCA is decarboxylated into THC and thus available for pharmacological activity in the body. This explains the fact that you get higher from eating a gram of cannabis cooked into food, than if you were to smoke the same gram.
Secondly, when you eat cannabis it passes through your liver where it is converted to 11-hydroxy-THC before arriving at sites of action in your brain and CNS. The fact that 11-hydroxy-THC is a more potent agonist of the cannabinoid receptor, and the separate fact that the 11-hydroxy-THC more readily crosses the blood brain barrier, all play in concert to give the feeling that you are 'higher'.
This fact holds true for high THC cannabis which contains no CBD, which nullifies the supposition that the stoned effect is due to the effects of CBD.
-Chimera
Excellent post, i thought to add some details on CBN from personal research.
CBN does nor seem to be a breakdown product of THC nor CBD, as historically reported (and repeated ad nauseum). Testing of uniform samples over a period of a year show no increase in CBN's, in fact they decrease proportionally with THC and CBD.
CBN does have a very strong narcotic effect that can persist for as long as 7-8 hours. Anything over ~1.2% is going to have noticeable effects.
A high CBN strain (2.1%) strain i have observed, has a noticeable "sweaty leaf" appearance, with a profusion of bulbous glands on all bud leaf.