Why do people write like this?

"A calligraphic inscription unfolds sequentially as characters are traditionally written down a surface in vertical columns and aligned across in horizontal rows from right to left or left to right. An implied vertical axis at the center of each column serves as a coherence-generating constraint for the spatio-temporal structuring of the individual written characters."

The idea is a good one, but the expression is clumsy. I don't know whether the "as" in the first sentence means "while" or "since." The word "traditionally" would imply that it means "since." I also don't understand "constraint" in this context.