"Create PCB from a selected sheets." All sheets in an EasyEDA project are treated as being part of a single schematic and therefore are all converted to a single PCB.

Easiest way to do what you're saying is convert to PCB then delete out components you don't to use. I've done this on a tester design that uses the same schematic for multiple PCB's, but one has most of the schematic, the other has the remainder. When you do an import changes later on it will place all the components in the corner of the PCB design and you can easily re-delete them.