I just released first version of change to explain.depesz.com that displays buffer I/O information, as described recently.
You can see it in here.
There are two new columns in there, showing how much data given node read from disk, and how much it wrote.
It's definitely not 100% OK now, as you can see, speed and time is not always there, but generally it should work.
There is also summarized info in stats page of the explain.
If you'd notice anything wrong, please let me know, either by mail, or just make an issue on GitLab.