Hmmm. I haven't seen the images, but wasn't the executive also limited to one font size? The "th" in the memo looks smaller to me.
Though superscripting was possible, wasn't it still limited to only superscripting normal-sized text?
The superscripted "th" was a special character, a replacement for some other non-standard character. The IBM typewheel had more characters available than a standard typewriter.
I am impressed, however, with the side-by-side comparison. I've done typesetting since high school shop class fourty years ago. I would not have expected the alignment to be so perfect between two different sets of type (typewriter and word processor). Computer fonts are not identical to typerwriter of lead fonts. Each time a font is created there are tiny differences. If you were going to create an electronic font you would probably start with a high quality scan of lead type, not the output of a typewriter with a plastic ball.