He's using the `show` parameter which does include tags. However you can't really grep it like he had done because the tags can span multiple lines with indentation rather than line prefixes (ie human readable rather than machine readable).

apt-cache show doesn't show tags for me:

  $ apt-cache show aria2 | grep Tag
  $ echo $?
  1

Does on Debian and has done for a few releases as far as I can recall. I've done it on Wheezy (7.x) boxes and it's still there on an Jessie (8.1) machine I just tested it on.