I am suprised Microsoft haven't been including this on all plans for FREE never mind for a monthly fee, even the cheapest plans from OVHcloud or Linode comes with DDOS protection included in the price. Or the free tier on Cloudflare if you just want to protect a website from DDOS attacks.
It sounds like Microsoft are milking their customers for a few more dollars by making them pay for what is an essential service on the modern internet.