Is it necessary to introduce a new variable here? (MDN strings tutorial)

I'm a total newbie to computer science. I beg for patience.
I've been following this tutorial and I'm on the first "active learning example."

const list = document.querySelector('.output ul');
list.innerHTML = '';
let greetings = ['Happy Birthday!',
                 'Merry Christmas my love',
                 'A happy Christmas to all the family',
                 'You\'re all I want for Christmas',
                 'Get well soon'];

for (let i = 0; i < greetings.length; i++) {
  let input = greetings[i];
  // Your conditional test needs to go inside the parentheses
  // in the line below, replacing what's currently there
  if (greetings[i]) {
    let listItem = document.createElement('li');
    listItem.textContent = input;
    list.appendChild(listItem);
  }
}

The goal is to modify the above code so the live output will display only the array values that include 'Christmas'. This is my solution:

for (let i = 0; i < greetings.length; i++) {
  let input = greetings[i];
  if (greetings[i].indexOf('Christmas') !== -1) {
    let listItem = document.createElement('li');
    listItem.textContent = input;
    list.appendChild(listItem);
  }
}

This is the tutorial's solution (the same except for the introduction of a new variable - "result"):

for (let i = 0; i < greetings.length; i++) {
  let input = greetings[i];
  if (greetings[i].indexOf('Christmas') !== -1) {
    let result = input;
    let listItem = document.createElement('li');
    listItem.textContent = result;
    list.appendChild(listItem);
  }

Is it necessary to introduce "result", when it's just going to be changed to "input" anyways?