migrations Issue in Many to Many table when generating migrations from an existing database

This is a (multiple allowed):

[x] bug
[ ] enhancement
[ ] feature-discussion (RFC)
CakePHP Version: 3.5.10
Migrations plugin version: 1.7.2
Bake plugin version (if relevant): 1.6.0
Database server (MySQL, SQLite, Postgres): 5.7.20-0ubuntu0.16.04.1
PHP Version: PHP 7.0.22-0ubuntu0.16.04.1
Platform / OS: ubuntu0.16.04.1

What you did

I tried to prove the generation and import of a simple datable with a belongstomany relation: books---<books_words>---words first I've tried to generate the table with

bin/cake* bake migration_snapshot Initial* when the book_words is generated the primary_key is blank

Expected Behavior

         $this->table('books_words', ['id' => false])
            ->addColumn('values', 'string', [
                'default' => null,
                'limit' => 45,
                'null' => true,
            ])
            ->addColumn('word_id', 'uuid', [
                'default' => null,
                'limit' => null,
                'null' => false,
            ])
            ->addColumn('book_id', 'uuid', [
                'default' => null,
                'limit' => null,
                'null' => false,
            ])
            ->addIndex(
                [
                    'book_id',
                ]
            )
            ->addIndex(
                [
                    'word_id',
                ]
            )
            ->create();

Actual Behavior

         $this->table('books_words', ['id' => false, 'primary_key' => ['']])
            ->addColumn('values', 'string', [
                'default' => null,
                'limit' => 45,
                'null' => true,
            ])
            ->addColumn('word_id', 'uuid', [
                'default' => null,
                'limit' => null,
                'null' => false,
            ])
            ->addColumn('book_id', 'uuid', [
                'default' => null,
                'limit' => null,
                'null' => false,
            ])
            ->addIndex(
                [
                    'book_id',
                ]
            )
            ->addIndex(
                [
                    'word_id',
                ]
            )
            ->create();