Hmm, if it didn't look so new I might think it was a type of flooring that was common in the mid-20th century known as magnesite, also called "Diato" I believe. That was a mineral pour-in-place material that was often used to protect concrete decks and other outdoor (and indoor) floors and structures, like stairs.
I don't see any chance for you to try to fix this with it being un-noticeable. The closest you might get is to use a hard-setting repair plaster to fill just below the level of existing, then buy some paint to match, add aggregate to try to match the anti-slip treatment on there, and brush/roll to blend. I still think it will show, and it might crack around the repair because different materials tend to do that due to different flex, expansion and contraction properties.