Why doesn't the new English grammar course use the traditional term non-predicate verb?

The answer is as follows:

There are different schools of English grammar, including traditional English grammar, functional English grammar and structural English grammar. Their grammatical terms are different. Because New English Grammar Course belongs to functional English grammar, there is no non-predicate verb in functional English grammar. Gerund and present participle are collectively called -ing. In traditional English grammar, there are such grammatical terms as non-predicate verbs, gerunds and present participles.