Soldering a EPC2204A GANFET?

They have a rectangular silkscreen mask not soldermask which must block solder between pads.

yes you are right, but they are also "solder mask defined" pads....apparently this is crucial for these "solder ball" pad fets.
........from the explanation of how to solder the EPC2204A, it looks like if a single microscopic grain of dust got into the PCB assembly factory than it would be a total disaster.

I used a ball grid array version. Treated it like a FPGA. It pushed the PCB house and everyone, but it works.