Is this maybe related to performance of the server running the document server? The network might also be the reason. When We work with docs it saves within 0.X to 1.X seconds. Depending on the doc size.
I think he is talking about the doc saving from OO to seahub, rather than saving in the OO.
It does take longer time for OO to push the update to seahub (same experience at my side). I think the reason is that OO uses some timeout mechanism to determine if the user closes the doc. After that, it push the updated file to seahub at once.