Yes, that is one of the possible explanations for trichomes. However, In literature there are several potential reasons for cannabis producing THC listed, some of them are:

-deterring certain insect and other herbivores -Anti-microbial effects -UV light protection

Claiming that heat shock defense is the only reason seems like a simplification, considering that scientists are still researching the matter.

It used to also be insect deterrent but since we've bred cannabis to have so much lovely THC that the globules are too large and dry to work. But that's ok because cannabis has domesticated humans enough that we've invented climate controlled hothouses to grow them in.