You can put tokio in single-threaded mode if you prefer - it's an explicit performance tradeoff. The multithreaded work-stealing executor has higher throughput at the expense of needing more synchronisation.

Or you can schedule your thread-local tasks in a LocalSet to run them all on the owning thread, while keeping the other threads around to handle tasks that are intentionally parallel.

The general theme here is that tokio (and C++ equivalents) provide you the flexibility to do more things than the native Python/Node runtime does (and yes, the defaults take advantage of this). But the underlying intention is the same (and post-GIL we expect to see some movement in this direction on the Python front as well).