> The placement of keys in such s way that they had a low probability of jammin

It's highly debatable, and arguably a myth. The QWERTY design predated any potential jamming problems. Perhaps it was so foreseeing? It's really hard to believe general ergonomy was the top priority, as all the characters of the word TYPEWRITER are placed in the top row, which could have hardly happened by sheer coincidence, but was very convenient for the sake of sale presentations in the early years...