I am curious how this differs conceptually from "Basic English" which always struck me as quite linguistically naive. English is full of prepositional verbs like "shut up" that have a specific meaning that you have to just memorize. So when you're listing out the "vocabulary" of some reduced version of English, you have to count "shut" "up" and "shut up" as different words. Or "break up with" to mean to end a romantic relationship. It's a set phrase with a defined meaning, not just a phrase whose meaning is apparent from the words used. It needs its own entry in a dictionary.

edit: Not to mention compound words in English, which any linguist would say are just one word ("hot dog") but because of spelling conventions, people tend to parse as two words. (In English, you can tell when something has become a compound noun by the stress pattern; John McWhorter calls this "backshift" and it's also the difference between the noun and verb forms of words like "record" and "rebel.")