Doing something like:
$user->name = 'user ' . date('H:i:s');
$user->save(['timestamps' => false]);
Results in:
'name' => 'user 12:36:35'
'updated_at' => '2016-05-02 12:36:35'
The reason appears to be that, although in the model's performUpdatemethod the updated_at column is discarded, Illuminate\Database\Eloquent\Builder adds it again.