Looks like that might have changed, libc-gconv-modules-extra has an i386 package for 2.42-5 added at like midnight UTC+1. Given the sources only update every 6 hours, might be you found an unlucky update in between?

Struggled to find a time for the release, but the changelog has one, unsure how true to package-available time that is:

glibc (2.42-5) unstable; urgency=medium

  [ Martin Bagge ]
  * Update Swedish debconf translation.  Closes: #1121991.

  [ Aurelien Jarno ]
  * debian/control.in/main: change libc-gconv-modules-extra to Multi-Arch:
    same as it contains libraries.
  * debian/libc6.symbols.i386, debian/libc6-i386.symbols.{amd64,x32}: force
    the minimum libc6 version to >= 2.42, to ensure GLIBC_ABI_GNU_TLS is
    available, given symbols in .gnu.version_r section are currently not
    handled by dpkg-shlibdeps.

 -- Aurelien Jarno <aurel32@debian.org>  Sat, 06 Dec 2025 23:02:46 +0100

glibc (2.42-4) unstable; urgency=medium

  * Upload to unstable.

 -- Aurelien Jarno <aurel32@debian.org>  Wed, 03 Dec 2025 23:03:48 +0100