Safari datetime-local form validity bug after unsetting value

Using the following form in Safari, if you set a date and then use the “clear” button to unset it, Safari will invalidate the form even though it’s valid.

It also doesn’t assign the input element with a validationMessage. Removing novalidate, all it does is select the day part of the input.

Am I missing something or is this a Safari bug? The form validates fine in Chrome.

https://jsfiddle.net/n_cholas/zfo9qm6p/27/

<form novalidate>
  <input type="datetime-local">
  <button type="button">clear</button>
  <button>Submit</button>
</form>

<script>
const form = document.getElementsByTagName('form')[0]
const input = document.getElementsByTagName('input')[0]
const btn = document.getElementsByTagName('button')[0]

btn.addEventListener('click', function(e) {
  input.value = ''
})

form.addEventListener('submit', function(e) {
  e.preventDefault();
  
  console.log('checkValidity', form.checkValidity())
  console.log('validationMessage', input.validationMessage)
})
</script>