We come across this a while ago but are still scratching our heads.
So what we have here is a typical house slab that has been excavated and poured, which was well below ground level. No major issue with the correct drainage and waterproofing strategy.
Then the builder took it upon himself to fill on top of the slab with what could only be considered a blob of concrete supposedly to make it easier for the Bricklayer. Now not only is it an extremely pointless, Non-engineered chunk of concrete but it also allows water to seep between the original slab and the concrete blob to flood the Laundry and lower media room with no simple way of waterproofing it. Those lines are saw cuts where the builder has attempted to saw cut and scrabble back his mistake before giving up.
Whilst there is a benefit to engaging a custom home builder who can provide you with the floor plan of choice and selection of finishes that are outside what your standard project builder can offer, also comes the risk of engaging a company without processes in place that may mitigate items such as this. As there are pros and Cons on both side please be mindful and do your research as to who you engage to build your dream home.