Is there an advantage of the operating system understanding the characteristics of how a thread may be used? For example, what if there were a way in Java when creating a new thread to indicate that it would be used for intensive CPU calculations vs will block for I/O. Wouldn't thread scheduling improve if this were a capability?
I'm not sure what you're actually expecting the OS to do with the information that a thread is I/O or compute. The things which actually make the most difference to how threads get scheduled (ie thread priority and thread CPU affinity) are already exposed by APIs (and support for NUMA aspects are starting to appear in mainstream OS APIs too).
If by a "compute thread" you mean it's something doing background processing and less important than a GUI thread (from the point of view of maintaining app responsiveness) probably the most useful thing you can do is lower the priority of the compute threads a little.