I got very confused because a JSON generated double-quote (") character doesn't match <U+0022>. Even if you use \u0022 to generate it.
I tripped over this when trying to manually parse a JSON string, and finding that I couldn't search for a quote character that I had a generated using <U+0022> instead I had to let JSON generate the quote character using \" or \u0022.
(click diagram for source)
JSON and PREPROCESSOR quote characters display identically but can't be compared.
(PS it would be useful to have the \" escape string outside of JSON rather than having to use <U+0022>)