The deal is that whenever the plant is heated to 180 degrees, the cellulose turns to alcohol.
That would make smoking unknown weed quite hazardous (hence the reference to a Richard Pryor moment).
Growers are currently able to keep their strains shielded from low-THC strains. What makes you think they couldn't do the same with the recombinant plants?
Maybe they can hit the jackpot and get a plant that produces substantial amounts of cyanide when burned.