Document.populated() & Document.$getPopulatedDocs() not work when populating Virtuals in Query

[L-Trump]

    let doc = await this.mainModel.findById(frameId).populate({
      path: 'position'
    });
    console.log(doc.populated('position'), doc.$getPopulatedDocs()); // undefined, TypeError

However, populate by Documents works

    let doc = await this.mainModel.findById(frameId);
    await doc.populate({
      path: 'position'
    }).execPopulate();
    console.log(doc.populated('position'), doc.$getPopulatedDocs()); // truthy value, [doc]