In two weeks from now (week of April 26th, 2020) we will update the way I/O Runtimehandles activations for successful blocking invocations.
This is the new behavior:
By default,successful blocking invocations will not produce an activation record, thus running “wsk activation list” will not list any of these. Logs are still recorded and can be retrieved using the activation ID - this is still being sent to the client invoking the action
Blocking invocations that failed will produce an activation record and will appear in “wsk activation list”
Developers can force creating an activation record for successful blocking invocations by including this header “X-OW-EXTRA-LOGGING: on” in the request
Non-blocking invocations don’t change, “wsk activation list” will return all the activation IDs created by non-blocking
Public docs have been updated 
You might ask why we are doing this change: performance and developer convenience. We can squeeze more performance by dropping the activation record, so the total duration for the invocation is smaller. Second, for customers who have millions of invocations per day it is not convenient to filter through all those activation records in the search of that one activation that failed.
Finally, we didn’t just decide this and went for it. We talked with some of you to validate that this change has a positive impact and that your workflows are not going to suffer.