It seems that Warner Bros Games have made a decision very similar to Bethesda with their Nintendo Switch ports by adding additional downloads.

Mortal Kombat 11 on Nintendo Switch will take up 6.54GB of your storage but then will then receive a massive 15.9GB day one patch.

Check it out below:

huh, base game is only 6.537GB, update is the bulk of it
gotta love @WBGames fuckery

— Nikki™ (@NWPlayer123) April 9, 2019

This is likely because Warner Bros Games wants to use a 8GB cartridge for the physical edition of Mortal Kombat 11 rather than a 16GB or 32GB cartridge due to it being cheaper.

It is a shame but this seems to be a common practice with Bethesda making users download all of Wolfenstein Youngblood in the physical edition and even Capcom making you download a whole game in the Mega Man X Legacy Collection!

If we have any more information to share we will cover it here at NintendoSoup so stay tuned for more!