Question about index sorting and accented characters

[Gavin Smith]

If in an input file I have

\input texinfo


@node Top
@top

@cindex @'e @'e

@printindex cp

@bye

And then I run

texi2any test.texi --html --no-split --disable-encoding

the output file has a letter heading "E":

<tr><th><a name="Top_cp_letter-E">E</a></th><td></td><td></td></tr>

But with

texi2any test.texi --html --no-split --enable-encoding

I get a heading "É":

<tr><th><a name="Top_cp_letter-É">É</a></th><td></td><td></td></tr>

I believe this is out-of-scope for the --disable-encoding option, as
the manual says:

'--disable-encoding'
'--enable-encoding'
     By default, or with '--enable-encoding', output accented and
     special characters in Info and plain text output based on
     '@documentencoding'.  With '--disable-encoding', 7-bit ASCII
     transliterations are output.  *Note @documentencoding::, and *note
     Inserting Accents::.

Nothing there about letter headings in HTML.

Would I be correct in thinking that "E" is the correct heading to use?

"E" would be used if the index entries were sorted with sort keys that
only included ASCII characters (no accented characters, for example).
As far as I remember, that's what texinfo.tex and texindex do.