Yes, node.js javascript runtime is based on V8, the same that runs in Chrome. Javascript is single threaded so anything that is not I/O bound will block the main thread. If you don't want to block the thread becasue you have long running calculation/parsing task, then you can use worker threads[1]. This will run your task in separate thread and not block the main one.
[1] https://nodejs.org/dist/latest-v12.x/docs/api/worker_threads...
It's a really annoying problem, and I'm actually really happy to see that many others have the exact same thoughts I had at the time, and that I wasn't just missing something obvious!
For example: https://github.com/nodejs/node/blob/master/src/node_crypto.c...
I generally use that as an example when explaining to people why Node isn't a great fit for a lot of workloads. They have to use these features internally, but you as the user with a CPU-intensive job don't have access to those features.