Does React component definetely update itself when a method is called - meteor

Question

Although you don t need to look at the code below to understand the question, I added it in case you need to visualize the scenario. Whenever the form submits, addList method is called.
And the component updates itself. But I didn t expect this behaviour, that s why at first I did try to assign my lists to state, so that when the state changed the component would update itself as I wanted.
Anyway it already updates itself, but why ? Which way is more efficient ?
import React,{Component} from 'react';
import TrackerReact from 'meteor/ultimatejs:tracker-react';
import {Lists} from '../lib/collections/lists.js';
export default class App extends TrackerReact(Component) {
constructor(){
super();
// this.state = {lists : this.lists()}
}
lists(){
return Lists.find().fetch();
}
addList(e){
e.preventDefault();
//let text = this.refs.list.value ;
let text = this._inputList.value ;
console.log(this._inputList.value);
Lists.insert({
title : text
});
this._inputList.value = "";
//this.setState({lists : this.lists()});
}
render() {
return (
<div>
<h2>Lists</h2>
<ul>
{this.lists().map((a,b)=>(
<List key={a._id} title={a.title} />
))}
</ul>
<form onSubmit={this.addList.bind(this)}>
<input
type="text"
ref={(input)=>{
this._inputList = input ;
}}
placeholder="add list bro"
/>
</form>
</div>
)
}
}

Answer 1

So if we add a componentWillUpdate react life-cycle method to see if it rerenders ;
componentWillUpdate() {
console.log('will update');
}
When form submitted "will update" is logged on console as expected. However if we update addList as ;
addList(e){
e.preventDefault();
// nothing else.
}
We don t see the output "will update" on console. Which means method being called doesn t require the component to be rerendered. There is no such a rule. In this case , it is probably about TrackerReact. TrackerReact might force the component to rerender.