[lilactown]

It depends on your perspective.

The OS one has more _requirements_ (the number of "it must do..." is much higher), which constrains it's design space much more. I think you can call that as "having more constraints" because it must meet more needs to be even viable as a solution.

The number of requirements for JVM threads is much lower, thus less constraining, allowing it more freedom to implement solutions that can meet its narrower window of features.