No judgment here, and to be clear I don't mean to invalidate her suspicion or yours. It wouldn't surprise me if there were unethical individuals in HR who take things like this as an opportunity to call out things they don't like... But in my experience, the asking part is pretty typical, and I doubt it was targeted.

For me, I-9 verification was very early on in the onboarding process. A list of eligible I-9 documents was provided in the onboarding paperwork and HR scheduled a time in my first day or two to show them on camera. Took maybe 2 minutes once we were actually on the call.

I didn't press them on why when asked to unblur, but given I-9 is about presenting documents that verify your identity / eligibility to work, I suspect it's best practice to avoid any obvious image processing as a matter of policy. At the very least, not having to worry about the paper getting blurred just makes things easier. Ultimately, they're keeping these images on file to cover their own ass, so they want them to look as clear and legitimate as possible.