And the second article elaborates on what "sold-in" means - it means sold to retailers, not necessarily sold to end-users/consumers.
Bought and sitting in a warehouse amongst other possibilities are included in that 5 million figure. That's not 5 million sold to consumers that they've got sitting underneath their TV like your open-ended "sold" phrasing is attempting to imply.
It's a very open-ended figure though, it's POSSIBLE all 5 million are "sold" in the sense you're implying - but there's nothing there that evidences it - in fact they phrased things to explicitly make it clear they're not stating that 5 million were sold to consumers. But if 5 million shipped to retailers and all did sell, they could quote the same. (As well as if say only 15 of them sold worldwide, but retailers bought 5 million - it's a pretty worthless figure on its own for what you're trying to use it for)
On "retailers buying them" - sure they did, but that's comparing apples to oranges against other figures - generally speaking that's referred to as "shipped" in most figures, "sold" refers to those bought by the end user normally. "Sold" in the PS4 context is in consumers hands for example where it's always been separate from the "shipped" figure the few times they've mentioned it.
With the games mentioned earlier, games "sold" are sold at retail to consumers, not sold to retailers. Ad nauseum. Or in short - use the word shipped for the 5 million figure if you're going to try to apply it equally, because that's the common vernacular.