Correct. If you look at the block diagram of the AD9084 (from the article link), it has on-chip DUC (Digital Up Converter) and DDC (Digital Down Converter) blocks.

https://www.analog.com/en/products/ad9084.html

That's not really true, there's plenty of applications that use these sort of bandwidths. A big one is optical communications (28 GHz bandwidth is actually not super high there), but also some specialised microwave comms and radar/military. They alm do processing at 10s to 100s of GS/s (obviously highly parallel).

While full bandwidth applications certainly exist, it is rare. Most direct sampling schemes are used for having a purely digital RF front end within the Nyquist range of the ADC/DACs. It's cheaper and easier to develop firmware/gateware than debug analog RF issues and respin hardware.

That's not even crazy considering you can do tens of Teraflops/s on modern GPUs.

Get your data into the system via PCI-E, do some RDMA magic to get the data onto your GPU and put the cores to work.