Yeah a little of that! We reuse IPv4 addresses when people delete apps and free apps churn pretty frequently. You never know how someone dirtied an IP.
Free services attract people who are prone to getting DDoSed. We mitigate DDoS attacks a whole /24 block at a time. Today’s issue was caused by a DDoS mitigation bug. You won’t notice most DDoS attacks, but it’s still worth avoiding higher risk IP space.