Why would having an FPGA mean automatically mean it’s smoother and more accurate? CW40’s 12000 mm/min and a resolution of 0.001mm is more than any hobby level mill or router is likely to achieve in the real world. It has a more expanded control set and much more I/O and runs no less smoothly on identical machine using same parameters as the DDCSV. It shouldn’t need to be hack able when the software and firmware are up to scratch ;)
It's simply the way the step generation works. An FPGA can do many parallel tasks at the same time and take load off the CPU. There is also way more accurate timing since the CPU is not shared between G-Code decoding, screen updating, user interface tasks, USB stack, operating system and then the real time step generation.
In the DDCSV1.1 the CPU sends blocks of motion data directly to the FPGA that handles the entire step generation process smoothly and in parallel.
Also, I would not really trust any specs on Aliexpress or other Chinese sites. They are often multiplied by a factor between 2 and 10.
Not all vendors do that, but many definitively do.
Apart from that, there is jitter and other bad effects from CPU based step generation, that are (almost) not present when dealing with an FPGA driven system.
Chinese software is never up to scratch. They make very good hardware, but the software very often is just really poor.
I am sure this may improve over time, but we are not there yet at all. Again, this does not apply to everything, but to a rather large amount of products.