And in more detail why you need it. Want to test a trading robot?
I am developing a crypto tax calculator
he explained it quite clearly in the first post
he's writing an automated tax report
Why don't you do it yourself and determine the conclusions of your research.
maybe because registering and using those exchanges requires user to pass KYC procedure
that would take too much time and effort to create himself an account on every single exchange
so he expects someone who already has those accounts can share "read-only api keys" for some $$