They won't do anything after you've sent a selfie anyway. Same thing happened to me. They'll ignore all of your contact attempts. IG support is pretty much non-existent.
edit: whoops, I misread the parent. I swear I know the difference between various IP types!
And depending on what you mean by "lose liability protections" for ignoring valid takedowns, I'm pretty sure that applies to the specific item and they don't stop being a safe harbor in general.
I sent in the selfie and haven't heard back in over 6 months.