It's called "units in transit." Sony doesn't wait for counting a sale for them as a company until a PS5 unit has arrived at a store. Once an order has been placed and has been sent underway, it's already sold for Sony a.k.a. shipped.
You used the wrong link in your article, yours leads to Sony's Q3 results. This is the correct one for Q4 and the full year:
And here is the more detailed one that lists PS shipments on page 9:
Thank you. It was really late last night when I wrote that and forgot to update that link to the latest quarter.