As noted in the doc, failover occurs ONLY with HTTP clients that use the wM IS API. Which IME, is nothing – I’ve never seen anyone use the IS client libraries. No other clients support doing that and the server has no role in this failover. It is entirely up to the client using Context/TContext to see the error and resend, which will go to the other node. It has been this way ever since I can remember.
That description does not indicate that a service that is in the middle of executed can suddenly jump to running on another node. It is akin to the checkpoint and resume behavior @Percio_Castro1 describes.