The Elisp manual node "(elisp) Interpolated Strings", which documents
the function format-spec and is new in Emacs 27, is currently included
under "(elisp) Text", which opens with:

  This chapter describes the functions that deal with the text in a
  buffer.  Most examine, insert, or delete text in the current buffer,
  often operating at point or on text adjacent to point.  Many are
  interactive.  All the functions that change the text provide for undoing
  the changes (*note Undo).

I think a more appropriate location would be following "(elisp)
Formatting Strings", or at least under "(elisp) Strings and Characters".

Patch for emacs-27 attached.  WDYT?

Thanks,

--
Basil

In GNU Emacs 27.0.91 (build 7, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2020-05-27 built on thunk
Repository revision: 9d7fd78421a339f00892b3241845b1024e2eff7d
Repository branch: emacs-27
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux bullseye/sid