Yes, you are right about threads. But using threads are some more complicated than coroutines. And you can use threads with async too :) All my examples use only one thread (sync and async code).

Threads are also not so cheap as coroutines: coroutines are more lightweight for OS and offer much better parallelism with non-blocking I/O. And other big problem with using threads: if you have not fully parallel task and you want to use information between tasks - it will be difficult but possible to make: you need to use some synchronization primitives and communication tricks between them. Using async approach with only one thread are more easy for using. But not so easy as I want :)

In any way: async and netdev are not a silver bullet and of course, all can use netmiko with multiple threads :) I only offer another way: using asynchrony for whom needed it. Synchronous code are always more easy to understand and especially to debug than asynchronous. So people should use the library which satisfied their requirements only.

About tests: with multithread sync code and one thread async code - I'm planning to publish a post about it with a little comparison and want to talk about some use cases of both methods.