为什么 Redlock 算法说“It tries to acquire the lock in all the N instances sequentially”

在Distributed locks with Redis – Redis - The Redlock algorithm中，它说

It tries to acquire the lock in all the N instances sequentially, using the same key name and random value in all the instances. During step 2, when setting the lock in each instance, the client uses a timeout which is small compared to the total lock auto-release time in order to acquire it. For example if the auto-release time is 10 seconds, the timeout could be in the ~ 5-50 milliseconds range. This prevents the client from remaining blocked for a long time trying to talk with a Redis node which is down: if an instance is not available, we should try to talk with the next instance ASAP.

sequentially 是什么含义？为什么要 sequentially 呢？

然后在Distributed locks with Redis – Redis - Retry on failure中，它又说

When a client is unable to acquire the lock, it should try again after a random delay in order to try to desynchronize multiple clients trying to acquire the lock for the same resource at the same time (this may result in a split brain condition where nobody wins). Also the faster a client tries to acquire the lock in the majority of Redis instances, the smaller the window for a split brain condition (and the need for a retry), so ideally the client should try to send the SET commands to the N instances at the same time using multiplexing.

这不是互相矛盾吗？还是我哪里理解错了？