findOne passing primary key with join returns array

Summary

findOne returns an array when a primary key is passed and it's called with a join

Example

Code demonstrating the behavior

db.orders.findOne({id: orderId});  // returns an object

db.orders.findOne(orderId);  // returns an object

db.orders
   .join({
      orderLines: {
         relation: 'orderLines',
         type: 'LEFT OUTER',
      },
   })
   .findOne({id: orderId});  // returns an object

db.orders
   .join({
      orderLines: {
         relation: 'orderLines',
         type: 'LEFT OUTER',
      },
   })
   .findOne(orderId);  // returns an array

Expected behavior

Passing a primary key with a join should return an object. Passing the primary key should have the same behavior as passing a criteria object with id.

Additional context

Using Massive 6.9.0