Once upon a time, English had both singular and plural second-person pronouns; "thou/thee" and "ye/you" respectively. Over time, the use of the first three declined drastically, and "you" is the only one in popular use today.
English is relatively unusual in merging its second-person pronouns, although the use of the second-person plural in more formal or polite situations (aka the T-V distinction) is extremely widespread.
However, the matter of personal pronouns is such a fundamental aspect of grammar (at least in Indo-European languages) that it was literally the first piece of grammar introduced when we studied French. (It may not have been the first chapter, since the first chapter may have been limited to stock phrases and some pronunciation guides; it's been way too long). I find it highly implausible that any foreign speaker that has a working proficiency of English could somehow think that "you" is not used for both individuals and groups.
I have seen some very strange errors in English written by native Chinese speakers; however, it does seem implausible that every single person on their team interpreted the sentence in exactly the same wrong way.
https://en.wikipedia.org/wiki/English_personal_pronouns#Arch...
Chinese, however, still uses both singular and plural second-person pronouns; 你 (nǐ, lit. you) and 你們 (nǐmen, lit. you all) respectively.
https://en.wikipedia.org/wiki/Chinese_pronouns#Personal_pron...
Note that the above is drastically simplified and I recommend reading the links for more information.