The classical indica or hashplant might look more similar to some of the auto crosses where the whole plant is a 1-2 ft. single cola. Completely different than a sativa which will grow like a tree. It's easy to see how the hashplant phenotype is easily suited to indoor growing when space and light cost money. This is a big reason for many of the cannabis crosses at least old ones from years ago.
The "% thc" of the whole entire plant will be a higher number if you compare a hashplant to a 15 ft. tall plant, even if the flowers are potent. Since the sativa phenotype might give you mostly fiber stalks by volume/weight and relatively few potent flowers, understandable why this isn't as lucrative, or even viable really for suppliers let alone hobbyists. Remembering years ago when I heard about 7 week chop, it is really cool to see more and more "tastier" maybe lesser yielding strains 60-80+ days being grown.
I think I would replace "Classical" with "Modern" Classical Indicas or Hashplants from the 70s are usually moderately tall and quite bushy. The typical afghan plant is much taller than people expect, they have been conditioned by seeing pictures of plants grown in extremely poor soil and harsh conditions but if you look at something like a Mazar-i-sharif plant you can find giant hashplants in the mix.
But I'll agree that the selection for faster plants has made them smaller and IMO less interesting..
as for my opinion on small plants being frostier, I think it really depends on when in the veg process the plants starts flowering, I think that when the first layer of resin appears and the leaflets are closer to the buds you will see more resin. In the end if you average the trichome yield over the entire plant they will be similar