I did some similar testing a few days ago[1]. Comparing platform threads to virtual threads doing API calls. They mention the right conditions like having high task delays, but it also depends on what the task is. Threads.sleep(1) performs better on virtual threads than platform threads but a rest call taking a few ms performs worse.
The goal is to bring fast random read/writes to Java. Fun project with lots of great challenges around performance while maintaining a nice API.