A test measures you. A drill improves you. Free typing spends most of its time on keys you already own, so these do the opposite: each one isolates what actually costs you time, and rehearses only that. Work down the ladder, then take the test.
Hands, not vocabulary. Nonsense syllables on purpose — a real word can be typed from memory as one motion, which is the very habit these are trying to replace.
tab retry esc new text ctrl+backspace delete word