Thanks @ErnieS0 for the response!
I had a word with Fidelity, and it seems this backup withholding could be reverted if additional documentation is provided in W-8BEN in part II (Claim of tax treaty benefits(for chapter 3 purposes only) ).
Now, I'm having a really hard time figuring out what kind of income, technically speaking, the sale of stocks/etfs is so I can fill in the details sought in line 10 (screenshot attached). I referred to the India-US treaty document, but was left confused about the appropriate article and paragraph to choose. Any pointers on that?
