I looked around Tutorials and found two different
nodetypes, 'perltutorial' and 'document' (but have never
seen 'document' in newest nodes). Checking the nodetypes
is labor intensive (get id from title, then lookup with
node_id=37150&nodes=860,62782) so most were not.
This list only reflects what was seen in newest nodes for
a number of weeks. I understand there are many more
nodetypes, most of which don't show up on newest nodes, but
some that might. I can't say if 'tutorial' is a valid
nodetype, but since its on the list and doesn't cause a
problem am inclined to leave it (having also received some
official verification of this list).