The 79m figure is shipped as of march 31st 2018, this lines up perfectly with their forecast.
Its not sold through? a guy on resetera said "So for Sony, we have actual MAU, shipment and sell through numbers? Nice"
Necro-bump this 2020: http://gamrconnect.vgchartz.com/thread.php?id=229249
Bumb in 2021: http://gamrconnect.vgchartz.com/post.php?id=9047071