Isolated instances do not a period define. We can always find some example of someone who did something, but the point is it didn’t start like that.
For example, there was never a period when movies were made by creating frames as oil paintings and photographing them. A couple of movies were made like that, but that was never the norm or a necessity or the intended process.
I’ve seen exactly that. In one case, it was JPEG scans of handwriting, but most of the time, it’s a cursive font (which may obviate “handwritten”).
I can’t remember which famous author it was, that always submitted their manuscripts as cursive writing on yellow legal pads.
Must have been thrilling to edit.