[Plugin: Global Translator] It is not really SEO Friendly

On the Intro Page said:

Search Engine Optimized: it uses the permalinks by adding the language code at the beginning of all your URI. For example the english version on https://www.domain.com/mycategory/mypost will be automatically transformed in https://www.domain.com/en/mycategory/mypost

But not really, i have check my WP translate around 3x post from Chinese to English, and i rebuild the sitemap manually ,however, it doesn’t contain the translated Url on that.

So ,how does google index it?
You can check my blog : https://www.netatlantis.com