The first one about fear of diffraction at f/11 and higher apertures is one that Bryan Peterson also mentions in his Understanding Exposure book.
I have to admit I had to relearn this lesson after shooting for 57 years. Todays near focus telephoto lenses act like macros with a paper thin depth of field. Diffraction is easy to fix with tools like Topaz Photo AI but most of the image completely out of focus - not so much.