\u0000 in literals?

It appears that tests:

  turtle-syntax-bad-esc-03.ttl
  turtle-syntax-bad-esc-04.ttl

are exactly the same.

The both have the contents:

# Bad string escape
<http://example/s> <http://example/p> "\U0000WXYZ" .

As far as I can tell, sections 2.5.1 and 6.4 indicate that NUL (U+0000) is
a perfectly legal character as long as it is escaped via \u0000 or \U0000.

Why are these tests marked as negative syntax tests?

Also, I assume that one of them was to test \u0000 instead of \U0000 ?

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics