Yes, I'm aware that 4-tuples must be unique. And so, by having a LB and/or server bind to more than one IP address, you can easily overcome that limit.
It's quite common in Kubernetes deployments, where each server in a separate Pod binds to a separate IP address.
And, as I said before, with DSR, there's a broad diversity of client IPs, so a single server address doesn't typically cause concerns with 4-tuple exhaustion.