Issue while updating view Model using setter method

Example Code

// STORE
class Todo {
  @observable title = "Test";

  @action.bound
  setTitle(value: string) {
    this.title = value;
  }
}

// CREATE VIEW MODEL
const model = new Todo();
const viewModel = createViewModel(model);

viewModel.setTitle("Updated Test") 
console.log(viewModel.title) // Updated Test
console.log(model.title) // Updated Test

Here when we console the original model we expected title value as "Test" only but actual output is "Updated Test"

package versions:
"mobx": "5.15.0",
"mobx-react": "6.1.4",
"mobx-utils": "5.6.2",

Reproduce the example with the listed mobx, mobx-react, and mobx-utils versions, then start at the createViewModel entry point. Verify how calling the setter affects the view model and original model; done means the view model shows the updated title while the original remains unchanged.