Writing code for your FPGA is not the only thing that needs to be done. It needs to be embedded on a board with the right pinning, and it needs to communicate with the outside world as well, through protocols, registers and what not. . Also there can be embedded softcores like ARM, RISC or Nios® cores running their own firmware. And also your design needs to be verified. Using UVM or some other method.
This usually means that there is a lot of communication with other designers, within and outside your own discipline. Especially when designs get bigger this can become complex.
Dizain-Sync can help streamline these processes, and find solutions for bottlenecks and issues in your design flow.
Examples include: how to do proper data management when working in a large team, how to specify the hardware/software interfaces, how to deliver your design data to the rest of the team or the business systems, like PDM, PLM and ERP, etc. etc.