Pretty much. The way it is integrated is pretty novel though. It has special cases for the various low level networking APIs which uses the asynchronous versions of said APIs. This lets the threads block in a very efficient way and scale to 1M threads without much overhead.
In general the overhead of a thread is around 1kb compared to the 1mb system thread overhead. That's fantastic.
(https://a.co/d/1XGdjWQ is an Amazon link to Solaris Internals)