The best part of all is farther down than what you quoted. The centering was still manual. That is, the IBM Selectric Composer didn't help you with this at all. You had to manually compute the size of the character strings and position the printing point accordingly for each line. (This is an incredible amount of trouble for a guy who didn't type but was nevertheless typing a "file" memo on a typesetting machine not otherwise used in his office, a memo to go nowhere anytime soon.)
Two supposedly manually centered letterheads typed months apart on an electromechanical wonder from 1972 line up pixel by pixel on a computer. Not "closely." Exactly.