Why do you say that?
I don't recall the data mining files ever saying that the 19 DLC were going to be characters, specifically.
A skin pack of 3 for each of the 6 DLC in KP1 = 18 skins, plus Ninja Mime Johnny for pre-ordering.
I mean, for all we know they could also do a smaller KP like they did with Injustice 1 or do an MKXL type of thing where they release another set of 6, all at once, 3 to 4 months after Spawn drops.
It was stated time and again that the 19 DLC slots had the EXP filename which was for characters, and skins were in a different location in the files.
There was also a question in the files saying "Would you like to purchase Kombat Pack 3?" or something. While this ISN'T a confirmation in any way, it is proof that they are/were considering 19 DLC characters. And the 19th ISN'T Shao Kahn, he was referred to as 0 DLC character slot.
While some players are wondering if these DLC references may point to post-launch content aside from fighters, such as stages or skins, thethiny provides compelling evidence that suggests that they do indeed demarcate Mortal Kombat 11 characters. Specifically, the 19 DLC strings are listed immediately following the current roster, and they each reference "EXP," just as other character listings do.
The Redditor further addresses the question by indicating that skin listings in the game files include reference to "SKIN," and stage listings reference "BGND." Of course, all of this does not guarantee that the 19 DLC references will all ultimately materialize as playable characters, but it does seem to confirm that the references are at least in the proper format for that type of asset.