Not necessarily. The manual typewriter I had in the late '60s had a button that released the platen and let me move it freely from left to right.
Still, e.g., the "X's" in 6d and 7e align perfectly horizontally with each other, but not with the "s" in "August", nor vertically with "Hospital" or "Highway. The logical answer for this is that the checked boxes were computer "cut and pasted".
But they're not the same as each other. Are you arguing that someone copied and pasted two different checked boxes, rather than just using the same one twice?
If the model with the horizontal unlock you mention was not available in 1961, I suppose a typist using a manual machine could still gently push the carriage to the right slightly, because you could slide it easily to the right, but not to the left. Which means the person would have to "space bar" or "tab" past the check box, and then try to visually center the box to the type guide and type an "X" with the other hand. Rather hit and miss, which is what we see, but still possible, now that I think about it, even without the special horizontal unlock feature. Partially depressing the backspace key was probably a better solution.
By the way, with that horizontal unlock feature, how did you return to the original spacing setting, or were you able to get back at all once you unlocked it? When you unlocked and scrolled vertically, it was always tricky getting back perfectly to the original line because of parallax error with the see-through guides.
Perhaps I'm wrong on that particular point with the boxes; thanks, it's been a very long time since I had my first manual Royal.