We're noticing a higher than normal thread count (100+) and have 20 as a the maximum specified for the PRPCWorkManager. Is this just a reporting issue where the count is not displaying correctly or could this be a different issue?
The http requests will eventually arrive in the App Server, and will get assigned to a thread in the App Server's threadpool. It is indeed possible to have many webcontainer threads running for the same requestor based on the type of the request.
Verify what each of these requesters doing by reviewing these in SMA. It is possible to have many threads created for the same requestor.