The format for the "choice" statement is:

  choice 'prompt' "{sub-prompt sub-symbol}*" default-value

and the following is *not* legal config language (note the
positioning of the closing double quote):

  choice 'prompt' "{sub-prompt sub-symbol}* default-value"

It only happens to work because of a combination of accidental
side effects of the current parsers:

  *   unpaired sub-words inside the 2nd word are silently ignored
  *   the missing last word is silently treated as if empty