I understand, but often in English, "all" is added after "you" or even contracted into "y'all" to represent plurality.
Most language apps/teaching uses "correct/proper", generic language, not slang or regional variations. At least not until one is quite far along.
It just would not be useful since it is more limited.
For example where I live in the US, "you all" is not used at all to mean a general "you". It definitely means "all of you". "You all" meaning "you" is regional dialect/use.
And when I was in Europe it definitely was not thought in English, for regular use, classes .
More below: "Y'all is strongly associated with Southern American English, and appears in other English varieties, including African American Vernacular English and South African Indian English."https://en.wikipedia.org/wiki/Y%27all