Bug#905965: debian-installer: preseeding language fails

[Josua Mayer <josua.mayer97@gmail.com>]

Package: debian-installer
Severity: normal

Dear Maintainer,

I have been trying to fully automate installing debian on the SolidRun Clearfog through a preseed file.
However I cannot seem to skip the first two questions:
[!!] Select a language --> English
[!!] Select your location --> United Kingdom

I looked at the sample at https://www.debian.org/releases/stable/example-preseed.txt
To quote "# Preseeding only locale sets language, country and locale."

So I put the line 
d-i debian-installer/locale string en_US

but I still get to see the question after booting with
setenv bootargs "auto file=/hd-media/preseed.cfg"

For reference I have seen this problem with two versions of the debian installer for testing:
http://ftp.nl.debian.org/debian/dists/testing/main/installer-armhf/current/images/hd-media/hd-media.tar.gz
https://cdimage.debian.org/cdimage/buster_di_alpha3/armhf/iso-cd/debian-buster-DI-alpha3-armhf-netinst.iso

and the daily snapshot of today (12/08/2018)
https://d-i.debian.org/daily-images/armhf/daily/hd-media/hd-media.tar.gz
https://cdimage.debian.org/cdimage/daily-builds/daily/arch-latest/armhf/iso-cd/debian-testing-armhf-netinst.iso

Am I just doing it wrong? I have tried examining the output of debconf-get-selections --installer
but I couldn't find something helpful there.

Yours sincerely
Josua Mayer

-- System Information:
Debian Release: 9.5
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: armhf (armv7l)

Kernel: Linux 4.17.0-0.bpo.1-armmp (SMP w/1 CPU core)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)