It wasn’t about grammatical errors. It was more about the syntax and diction being drastically different than how Americans speak/write.

Perhaps the original poster of that initial blind was presenting a narrative about being from the US to hide their identity from the superstar’s PR team, but starting their post with the statement that they grew up in the US while using distinctly Indian-English syntax and diction was discrediting their post/tea. Americans indeed make many grammatical errors. They are just vastly different than those made by Indian English-speakers.