Inconsistency with info string with backtick

At the beginning of section 4.5, the spec states that

The info string may not contain any backtick characters.

However, just before example 85, it states

Info strings for backtick code blocks cannot contain backticks

Which implies that it may be permissible for a tilde code fence to have an info string containing backticks. This needs to be clarified to answer the question: what does

~~~ aa ```

compile to?