~ not followed by 0 or 1 should be an error condition per RFC 6901 #11

After reading RFC 6901 and going through the library code, I noticed a potential gap.

In the beginning of page 2 of the spec, the following is written:
"""
The ABNF syntax of a JSON Pointer is:

      json-pointer    = *( "/" reference-token )
      reference-token = *( unescaped / escaped )
      unescaped       = %x00-2E / %x30-7D / %x7F-10FFFF
         ; %x2F ('/') and %x7E ('~') are excluded from 'unescaped'
      escaped         = "~" ( "0" / "1" )
        ; representing '~' and '/', respectively

It is an error condition if a JSON Pointer value does not conform to
this syntax (see Section 7).

Note that JSON Pointers are specified in characters, not as bytes.
"""

If I'm not mistaken, the spec explicitly states that ~ should only exist if followed by 0 or 1.
It also states that failing to conform to this syntax is an error condition.

Is this something that passed by you while working on the library implementation, or does enforcing this not really matter, or did I misinterpret the spec?