The new camera phones have a mind of their own and will refuse to allow normal viewing orientation. Maybe a Moderator can rotate them for you....?
The other issue is lighting. You should review each photo to be certain it illustrates what you are describing, 'cause with bad lighting we have no idea of even what the portion is.
So, in general the table looks massive and well done from a distance. However, "good woodworking" practices should have been employed in the build. This means the table can not be rigidly attached to the aprons. It should be supported, but not fastened in manner that does not permit expansion or contraction of the top. The "Z" clips Steve suggested is a very common method. Elongated holes and washers is another.
Finally, if the boards used to make the top were not acclimated to room environments they will shrink and possibly split AND if construction lumber, 2 X 6's or w 2 X 8's were used directly from the lumber yard, that's exactly what will happen. Construction lumber is not dry enough to use in furniture in the dry environment of a house in the winter months.
It doesn't matter if pocket screws were used to secure them. However, if no glue was used, just the pocket screws it does make it far easier to replace a badly curved or split board. Some "distress" is allowable, and that's kinda up to the end user, in my opinion. It won't be or remain perfect, unlike "fine" furniture.
You do have a bit of a dilemma. If you are so unhappy with the final product, a return to the shop with GOOD photos may be one choice. You may ask to see other examples of tables they built to see what has happened in those instances. They will probably say, it's not their fault, it's the fault of the wood. But, if they used "wet" wood is is their fault. Rushing the product out the door results in the conditions you have described. I also imagine you paid a pretty penny for the table, and you should be satisfied, keeping in mind some distress is allowable.....