The "Send all applicable feeds to the device" will still check if the language is intended for the device by checking the device language setting.
Most devices in our organization use Danish as the device language, but some few use english.
We have made feeds for the 2 languages, and only the ones matching the device language is published in the agent on the device.
A Danish feed will only show up on devices configured for Danish, never on a device configured for English.
There should be a "general" feed language, that would be published to all devices, no matter what language the device is set up for.