(last updated: 12/28/17)
During the feudal ages, many people realized that fisticuffs against a heavily armed and armored warrior was tantamount to suicide, and as a result many of the major soft styles of fighting were invented. Throw represents a fighter's familiarity with joint manipulation, takedowns and slam techniques. Specializing in Throw techniques means to be able to seize and use leverage against an enemy, oftentimes using their own bodies against them. While a good deal of physical strength lies in being able to pick up an object, throwing it effectively requires technique and talent, not strength.
Throw is more of a technical measure of fighting than a strict measure of any physical acumen. Much like many other competencies, a very small person can be just as proficient with throwing as the very large. Additionally, a large character is not automatically good at throwing people--again, pinning someone down requires some level of technical knowledge. A large frame contributes to a high Physical competency, not the other way around.
That said, while Throw is connected to the fewest strict legendary feats, a master in Throw tends to have an extremely accurate sense of the weak points of people and structures--they can unbalance, subdue or even destroy with little more than a touch. Being able to throw someone through a building trivially is typically the hallmark of Throw mastery, but those who master Throw to the exclusion of all else could easily topple the same building with the same technique.