It certainly seems like a possibility. I think also that it struck them as the lowest-effort way to appease two separate camps:
1) Those who wanted old-school vibes
2) Those who wanted shorter adventures
There is probably a fair amount of overlap between these two groups as well. I also observe here on ENWorld that many who dislike the APs do so in part because of how involved they are - you cannot just pop open Out of the Abyss at the table and go, whereas you absolutely could do that with, say, The Sunless Citadel - you only need to skimread the dungeon and you're set.
Nevertheless, by putting the book out, they have produced a product that will fill a particular store shelf niche ("I want a book for tonight's game, easy to run") and which suits grognards and lovers of drop-in dungeon crawls. I am certain that they could have made something themselves to do all of this; but I suspect that the cost in man-hours would have been much higher. In fact, I suspect that Tales will be an exceptionally profitable book for them, all told; the cost of writing it is pretty minimal, sales appear strong, and it stands out from the rest of the books at the moment.