You are correct I swapped client with other such as worker, child, and helper,
In 2018, after a heated debate, developers of Python replaced the term. Python switched to main, parent, and server; and worker, child, and helper, depending on context.
The Linux kernel adopted a similar policy to use more specific terms in new code and documentation.
My problem with the term "slave" is that it does not indicate there is a delegation of work going, on but rather that the subdevice is somehow fully "owned" by the master device. Whereas in reality the master is more like a manager telling a worker what to do.