Tracked bug?

controllers.application\.js

import Controller from '@ember/controller';
import { tracked } from '@glimmer/tracking';
import { computed, action } from '@ember/object';
import { dependentKeyCompat } from '@ember/object/compat';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';

	@tracked _tag = 0;

  _id = null;

  @dependentKeyCompat
  get id() {
    this._tag;
    return this._id;
  }
  set id(v) {
    if (v !== null && v !== '') {
    	this._id = v;
      this._tag++;
    }
  }

  @computed('id')
  get watchedId() {
    return this.id;
  }

  @action update() {
    this._id = 'abc';
    this._tag++;
  }
}
import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
{{this.id}} - updates = {{this._tag}}
<br>
Watched: {{this.watchedId}}
<br>
<Input @value={{this.id}} />
<button {{on 'click' this.update}}>OOB update</button>
{{outlet}}
<br>
<br>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}