bug#49116: 28.0.50; Why `bound-and-true-p' is not working in lexical binding?

[Eli Zaretskii]

> Date: Sun, 20 Jun 2021 00:49:14 +1200
> From: Phil Sainty <psainty@orcon.net.nz>
> Cc: 49116-done@debbugs.gnu.org
> 
> (bound-and-true-p VAR) is syntactic sugar for (and (boundp 'VAR) VAR)
> which means that it works only for dynamic variables (i.e. variables
> stored in the value slot of a symbol).
> 
> Under lexical binding, function arguments are lexical variables, which
> means they are not stored in the symbol of that name, and hence cannot
> be detected with `boundp'.

Should this be mentioned in the doc string of bound-and-true-p?