In kernel/classes/datatypes/ezselectionezselectiontype.php, hasObjectAttributeContent always returns true.
Although this is correct for single choice eZSelection fields, it's not correct for multiple choice ones (where the user can publish content without any element selected).

In order to verify, in a template, if the attribute truly has content, the code below can be used. But it would be cleaner if has_attribute returned false when on item had been selected.

{if ne($node.data_map.ezselectionattribute.content[0], '')}
  {* has content *}
{/if}