We did spend some time contemplating teaching the platform about non-thread-based, i.e. asynchronous sequential composition, in the end we realised that if it walks like a thread and quacks like a thread, we might as well call it a thread.

If you read the JEP and play around with virtual threads (e.g. do asynchronous IO with CompletableFuture or blocking IO in a virtual thread and see what their exception stack traces look like and what their JFR profile looks like) you'll quickly see that the capabilities they offer were simply not attainable by asynchronous code, which is why we've spent years to teach the JVM's innermost mechanisms to be able to observe virtual threads and expose them to observability tools the same way as platform threads are (and how I know those capabilities weren't available before).

We've written and presented a significant amount of published material about virtual threads so there's not much point in recreating it here, but if you're interested, all that material is out there.

[1]: https://openjdk.org/jeps/444

[2]: https://docs.oracle.com/en/java/javase/21/core/virtual-threa...