Mongoose array setter/set not called on query

array.setter.test.js

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const schema = new Schema({
    strings: {
        type: [String],
        default: () => void 0,
        required: true,
        set: function(items) {
            console.log('strings setter called');
            for(let i = 0 ; i < items.length ; i ++) {
                items[i] = normalize(items[i]);
            }
            return items;
        }
    }
});
const Model = mongoose.model('Object', schema);

function normalize(url) {
    return url.substr(0, url.length - 1);
}

(function main() {
  const item = new Model({strings: ['first', 'second', 'third']});
  item.save();

  Model.findOne({strings: 'first'})
    .then(console.log)
    .catch(console.error);
})();

//Output:
// "strings setter called"
// null

//Expected
// "strings setter called"
// "strings setter called"
// [Object]