Strange relate behavior with objection

app.js

//From https://www.vincit.fi/en/blog/effortless-eager-loading-nested-inserts-objection-js/
//There's a bunch of code here that's not needed for this example, but I was trying to keep edits to a minimum
//Stick this in a directory, then `npm install objection knex sqlite3`
//to run: node app.js

//Changing reviewerId to reviewer in the code below will cause the problem I'm talking about 

'use strict';

const objection = require('objection');
const Promise = objection.Promise;
const Model = objection.Model;

const knex = require('knex')({
  client: 'sqlite3',
  connection: {
    filename: './test.db'
  }
});

// Make all models use the same database.
Model.knex(knex);

// Create the tables. Normally this would be
// done using migration files. For simplicity,
// we create them in this same file.
const createSchema = Promise.coroutine(function *() {
  yield knex.schema.dropTableIfExists('Movie');
  yield knex.schema.dropTableIfExists('Person');
  yield knex.schema.dropTableIfExists('Review');
  yield knex.schema.dropTableIfExists('Movie_Person');

  yield knex.schema.createTable('Movie', function (table) {
    table.bigincrements('id').primary();
    table.string('name');
  });

  yield knex.schema.createTable('Person', function (table) {
    table.bigincrements('id').primary();
    table.string('firstName');
    table.string('lastName');
    table.biginteger('parentId')
      .references('id')
      .inTable('Person')
      .index();
  });

  yield knex.schema.createTable('Review', function (table) {
    table.bigincrements('id').primary();
    table.string('title');
    table.integer('stars');
    table.string('text');
    table.biginteger('movieId')
      .references('id')
      .inTable('Movie')
      .index();
    table.biginteger('reviewerId')
      .references('id')
      .inTable('Person')
      .index();
  });

  yield knex.schema.createTable('Movie_Person',function(table){
    table.biginteger('movieId')
      .references('id')
      .inTable('Movie')
      .index();
    table.biginteger('personId')
      .references('id')
      .inTable('Person')
      .index();
  });
});

class Movie extends Model {
  static get tableName() {
    return 'Movie';
  }

  static get relationMappings() {
    return {
      actors: {
        relation: Model.ManyToManyRelation,
        modelClass: Person,
        join: {
          from: 'Movie.id',
          through: {
            from: 'Movie_Person.movieId',
            to: 'Movie_Person.personId'
          },
          to: 'Person.id'
        }
      },
      reviews: {
        relation: Model.HasManyRelation,
        modelClass: Review,
        join: {
          from: 'Movie.id',
          to: 'Review.movieId'
        }
      }
    };
  }
}

class Review extends Model {
  static get tableName() {
    return 'Review';
  }

  static get relationMappings() {
    return {
      reviewer: {
        relation: Model.BelongsToOneRelation,
        modelClass: Person,
        join: {
          from: 'Review.reviewerId',
          to: 'Person.id'
        }
      },
      movie: {
        relation: Model.BelongsToOneRelation,
        modelClass: Movie,
        join: {
          from: 'Review.movieId',
          to: 'Movie.id'
        }
      }
    };
  }
}

class Person extends Model {
  static get tableName() {
    return 'Person';
  }

  static get relationMappings() {
    return {
      parent: {
        relation: Model.BelongsToOneRelation,
        modelClass: Person,
        join: {
          from: 'Person.parentId',
          to: 'Person.id'
        }
      },
      reviews: {
        relation: Model.HasManyRelation,
        modelClass: Review,
        join: {
          from: 'Person.id',
          to: 'Review.reviewerId'
        }
      },
      movies: {
        relation: Model.ManyToManyRelation,
        modelClass: Movie,
        join: {
          from: 'Person.id',
          through: {
            from: 'Movie_Person.personId',
            to: 'Movie_Person.movieId'
          },
          to: 'Movie.id'
        }
      }
    };
  }
}

const runQueries = Promise.coroutine(function *() {
  yield Movie.query().insertWithRelated([{
    name: 'The terminator',

    actors: [{
      "#id": 'arnold',
      firstName: 'Arnold',
      lastName: 'Schwarzenegger',

      parent: {
        firstName: 'Gustav',
        lastName: 'Schwarzenegger'
      }
    }, {
      firstName: 'Michael',
      lastName: 'Biehn'
    }],

    reviews: [{
      title: 'Great movie',
      stars: 5,
      text: 'Awesome',

      reviewer: {
        firstName: 'Some',
        lastName: 'Random-Dude'
      }
    }]
  }, {
    name: 'Terminator 2: Judgment Day',

    actors: [{
      "#ref": 'arnold'
    }]
  }, {
    name: 'Predator',

    actors: [{
      "#ref": 'arnold'
    }]
  }]);

  let reviews = yield Review
    .query()
    .eager('reviewer');

  console.log(JSON.stringify(reviews, null, 2));

});

// Run the whole thing.
createSchema()
  .then(runQueries)
  .finally(() => knex.destroy());