Even on official MaterializeCSS page for Select when you select a value for multiple select you see the disabled selected "Choose your Option" and then the selected option(s).
It seems to me more user friendly to shoe only Option 1 as "Choose your option" is not a valid option.
I use the
<option value="" disabled selected>Choose your option</option>
so once page is rendered the user got a hint what is required of them.
Working jsFiddle.
It seems to me that using jQuery solves this issue (see an example) but I am using pure javascript only.
So the question is How to not display disabled, selected text for multiple MaterializeCSS select.
Copied from your js fiddle , this will fix your unselect issue.
function onSelectChange(s){
const elOptions = s.querySelectorAll('option')
elOptions[0].removeAttribute('selected') // this won't work
elOptions[0].selected = false; ///this will - tested //first option will be unselected
}