"the more you smoke, the higher you get" does not refer particularly to landrace genetics, but to the particular strain that the phrase was applied to. This 'no ceiling' effect is supposedly present in varieties with high measurements of THC (the percentage of which is measured against the prescence of only other cannibinoids, not in reference to the total percentage by weight) and low measurements of CBD, primarily, but also CBN and perhaps other cannibinoids as yet unknown.
Heres a little background info on what im talking about. Cannabis contains many different psychoactive compounds all referred to as cannibinoids. some people say there are as few as 61 of these, some say as many as 450 or even more. its not something the legitimate scientific community has spent much time studying. point of fact, only 3 of these cannibinoids can really be measured accurately: THC, CBD, and CBN. THC (composed of Δ8-THC, Δ9-THC, and THCV) is mainly what you get high on and has been recorded at being as much as 22%, perhaps 23% of the total cannibinoids contained inside the buds of a particular plant. Anything reported to be over this is probably a lie or promotional gimmick. CBD is supposedly what THC (and perhaps other cannibinoids) naturally degrades to over time, but is still present on freshly dried/cured buds, and it is usually found in concentrations of less that 2% of total cannibinoids in said freshly dried/cured buds. as THC degrades, it turns into CBD. for this reason, hashish commonly has a much higher level of CBD in relation to other cannibinoids, sometimes being more prevalent than all other cannibinoids put together. CBN is the only other cannibinoid that is measureable at this time. It is found in even smaller percentages than CBD, and its effects are as yet unknown.
These different cannibinoids all work together in a synergystic fashion to create the high you experience when you take a puff. Not much is understood about how all this works, but experience mixed with common knowledge and the few reputable studies done on this topic have shined some light in very recent years.
THC is what gets you high. all other cannibinoids serve to alter or change, in both good and bad ways, the high provided by the THC. It has been claimed that a high CBD level is responsible for the "creeper" high associated with some strains. a high CBD level may also create a "ceiling" where you just cant seem to get any higher no matter how hard you try.
A low CBD level in relation to a high THC level supposedly creates the effect you were asking about. More than one seed company claim this of Thai varieties, and perhaps it is true. Keep in mind, this is in no way "hard science," and as we only know about and can measure slightly less than a quarter of the psychoactive components contained in buds or hash. personally, i find strains like the one you are talking about to give relatively one-sided highs. Really up and motivated, fun if your gonna go out clubbing or to a concert, and some peoples personal favorites (all you haze lovers out there, Holla!). Personally i prefer a really good sativa/indica hybrid that has both the clear headed/ up high of a good tropical sativa and the deep stone junkie hashish body high associated with many hard-hitting indicas. you get the best of both worlds!