"Because vectors are typically written horizontally, we transpose the vectors to write them vertically".
Is there a typo in this sentence or is to just too early in the morning for me to read this?
No typo there. When we talk about vectors we mean "column vector". As it's easier to read horizontally (and takes less place in a paper), most of the time we write x^T = {a, b, c} rather than writing them in a column shape.