Have you noticed some of his letters to CAL are not in block capitals? This could give us a whole new insight.
A guy named Tom Garvey who has studied graphology has written this -
"Some may choose capital letters because it is important to be understood. They believe communication should be clear. Go one step further, they believe a writing is better than a spoken communication. Many will use cursive in letter writing but address the envelope in caps. Why? it is important that it is delivered. Take no chances with the post office that yours is undeliverable due to poor penmanship. Not a complicated question. The better question is why do people send illegible notes, letters, or instructions? they don’t care is the likely answer, you figure it out. If the writing on the envelop is very different than the contents you have a public persona vs. a private personal style. Many young people reading this may have never gotten a handwritten letter in the mail, too bad. they are a joy due to the personal touch, I miss them."