Titles aren't used as primary keys in the node table -- lots of nodetypes allow duplicate titles. The node_id column is the primary key.

I don't have the special PM source handy, but the newest Everything code has logic to redirect itself internally to a freshly-created node (by node_id, not title) whenever it encounters the 'new' opcode.

(Internally, titles aren't used much for the simple reason that they're not guaranteed to be unique.)