When filtering by host, only strings are recognized datatypes.

"filter":

{ "host": 'hostname' }

works whereas
"filter":

{ "host": ['hostname'] }

does not.

This seems to be caused by class.ctrigger.php:441
$sql_parts['where']['host'] = 'h.host='.zbx_dbstr($options['filter']['host']);

Should be:
$sql_parts['where']['host'] = DBcondition('h.host',$options['filter']['host'],false, true);