Redo size is not empty for select operation ?

Have you ever met situation that for “select only” operation “redo size” has different value than 0 in autotrace output?
It’s possible that sometimes we may face a bug and setting event 70150 or 71830 in database could fix this issue. One example below:

Simple count:

As you can see redo size in statistics part is 4345324

Let’s try to set some events:

And try to count again:

As you can see execution time is the same, however we didn’t use redo = “redo size” value is 0

Querying again – “redo size” still empty