Breaks Taxonomy menu. Entity translation should let 'und' as entity's language.

This is something I've never understood about Entity translation.
Correct me if I'm wrong but this module is about translating entities at field level, that is, there is one entity and several field translations for the different languages.
So why does Entity translation touch the language of the entity itself?
The language of the entity should be 'und' and only fields should have different languages.

Because of this, Taxonomy menu does not work well with translated entities: menu items show up for the source language but not for the others.
My case: I use both i18n taxonomy and Entity translation so that I can translate both term names+descriptions and attached fields.
The problem is that Entity translation requires to change the 'und' language of the term to a source language so that term's fields can be translated.
Because of this, menu items created by Taxonomy menu will get the same language and won't show up for other languages.

This is only an example, it could break all modules that check the core language fields of entities.
I really think Entity translation should not touch the core language field and add its own.