Capitalization

Q. These two examples are given in CMOS 6.81: “My name is Phyllis; that’s p-h-y-l-l-i-s.” “A proficient signer can fingerspell C-O-L-O-R-A-D-O in less than two seconds.” Why are the separated letters caps in one example but lowercase in the other?

A. Because both ways are commonly used, and both work well!

[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]