I have an at least 3-year old verified Bittrex account but I withdrew everything just a few months ago. I didn't receive such email. I guess they are more focused on accounts with balances than on those that are empty. They have nothing to gain with the latter, after all.
But you are extremely lucky for not complying and getting away with your funds. They must have missed freezing your funds there. After all, they do that even to those who complied.
Looks like you got the slightly "better" end of the KYC requirement.
[...]
Required: Please submit the following 3 images: An image of you looking directly at the camera, another image of you looking off to the right, and a final image of you looking off to the left. All 3 photos are required for all requests.
This is insane.
Things are getting more insane these days. From KYC to source of funds to mug shots. You name it. And not only on international platforms but also on local ones.
A month or two ago, I also underwent a confirmation process which asked me record a video turning my head around. I don't know what's that specifically for. They're just asking weird things. How I wish I could turn my head 360 degrees like a possessed man. That might have expedited the entire process.