To add, there is something about those old 40s and 50s era technical films like you linked that is just so… I don’t what exactly it is, but I find them fascinating and genuinely informative, even though they are explaining tech that is decades obsolete.
It’s pretty awesome that they are still available 70+ years later in excellent quality!
I actually prefer it the way it’s executed.
Maybe I’m thinking way too much about this, but each panel obviously takes some time amount of time to draw, and likewise each panel portrays some finite amount of time–not just an instant snapshot of the story. So as the dog is yelling at him, his drawing quality is degrading as he is working on the panel, leading to an inconsistent quality within the panel.