I've noticed a few component packages now that have small "tabs" on the sides of their exposed pad (thermal pad). One example is the Analog Devices ADM7154 LDO:
Note the 0.356 x 0.457 mm tabs on the left and right sides of the exposed pad.
I can't speak for all manufacturers, but sometimes thermal pad is the bottom of the die carrier, as that ensures thermal performance. Die carriers could be fed from a reel, that has stamped die carriers attached by thinner elements that are cut on unreeling. Those small tabs would be what remains of the die carrier holder.
You don't have to put the feature in the footprint, as it's likely solder won't flow well in the area, due to it's surface tension, but you shouldn't put exposed copper for other signals or vias there.
TL;DR:
The exposed pad, AKA paddle, is often used as a thermal interface to the PCB.
On the other hand, a lot of ICs that don't dissipate a lot of power, it's part of the package and often connected to some voltage rail such as ground. You'll find paddles on low power ICs typically on leadless packages.
Some ICs use paddles for high current connections and may have multiple paddles.
It's best to check the data sheet what you should do with this pad.
In your particular case, the paddle is used as a thermal interface as discussed on page 6 of the data sheet you linked to. Information on the PCB layout is shown on page 21, more thermal considerations on page 18.
The small tabs on the paddle are generally not part of the PCB footprint. You should used the manufacturer's footprint recommendation or lookup the footprint for a JEDEC MS-012-AA.
