bug#52839: 29.0.50; The '(declare (modes MODE...))' NEWS entry is confusing

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> Apart from changing the default value, that is.

That seems to be asking a question: what is the reason for the current
default value.  AFAICT this comes from:

    commit 927b88571cebb4f64aca360fbfa5d15a1f922ad6
    Author: Eli Zaretskii <eliz@gnu.org>
    Date:   Wed Feb 17 18:53:54 2021 +0200
    
        Disable filtering of commands in M-x completion
        
        This makes the default behavior like it was before:
        M-x completion doesn't filter out any commands.  To
        have commands filtered based on their relevance to the
        current buffer's modes, customize the option
        'read-extended-command-predicate' to call
        'command-completion-default-include-p'.
    
        * doc/lispref/commands.texi (Interactive Call):
        * doc/emacs/m-x.texi (M-x): Update the description of
        'read-extended-command-predicate' and improve wording.
        
        * etc/NEWS: Update the entry about
        'read-extended-command-predicate'.
        
        * lisp/simple.el (read-extended-command-predicate): Change default
        value to nil.  Update doc string.  Add :group.
        (read-extended-command): Handle nil as meaning to apply
        no-filtering.

But the commit doesn't say why this change was made (other than saying
"like it was before").  Was there a specific problem introduced by the
filtering, or was it a change based on a judgment call about what the
default should be to balance the tradeoffs between bringing new
features and surprising the users?


        Stefan "who doesn't have an opinion on this one"