https://nginx.org/en/docs/http/ngx_http_limit_req_module.html

> If the zone storage is exhausted, the least recently used state is removed. Even if after that a new state cannot be created, the request is terminated with an error.

Unless I misunderstood the intention, I think this should read: "… state is removed. If even after that, a new state cannot be created …".

That way it makes more sense.