While what you’re seeing is almost certainly a compression artifact or digitization difficulty (keep in mind, theater screens were the target media,) it was almost certainly a product of phototypesetting, so it would have to be inverted at least once. In phototypesetting, you’d load a large dark negative with a typeface developed into it into a phototypesetting machine. A typesetter would enter the text and whatnot into the machine, and the machine would locate the appropriate letter on the film using some kind of timing mark (the machines were all different) and as the letter passed over the target area, it would shoot light from xenon bulb through it to develop that letter, in the correct place, onto the target film. This is how a lot (most?) typesetting was done in the decades before digitized fonts were a thing. That’s how they got such nice clean lettering on posters and things like that.

I don’t know for sure, but they probably shot a negative of the completed type with a red gel behind it to get the final frames.