Dude... Everybody does that... It's like the ABC of text presentation...
Sorry... Didn't know you know (like... I guess not everyone here knows how to code). Anyway, though everything that formats texts is "string formatting" in the broadest sense (like, any method of embedding values or expressions into strings), indeed, that '"%s" % name' thing is quite old-school and probably a tell of Mr. DPC's background and age. As you put:
He could've done THIS (concatenation):
$ text_message_screen_list.append(["Hello, " + name, "How does you and me on Friday sound?", False])
OR (interpolation):
$ text_message_screen_list.append([f"Hello, {name}", "How does you and me on Friday sound?", False])
AND ALSO (not good for this case, but it has its uses):
$ text_message_screen_list.append(["Hello, {}".format(name), "How does you and me on Friday sound?", False])
(All are "string formatting" though more contemporary and Python-idiomatic... But the old-school way works the same and, if he's used to that, great for him... Won't harm performance--in fact, it only loses to f-strings--, but it has its limitations)