I’m using an image field here (I don’t recall which field types it happens with – perhaps all of them), and when the field has never been set before, its value as returned by get_field() is null. But when the field was set in the past, but now it’s unset, then the value is false.
ACF should return the same value in both situations.
There are times when you want to know if a value has never been set before. For example, if you want to use a default value if it has never been set, but if someone has edited the post and removed the default value then show nothing at all.
$value = get_field('some_field');
if ($value === NULL) {
// show default value
} elseif ($value) {
// show value from field
} else {
// show nothing
}
There are probably many conditions where it is important to know if a value has never been set or the field simply does not have a value.
