I spent the whole afternoon testing this issue in Lab and came to the following conclusions:
• When the FW has few Cores, the fwd process can be used by any CoreXL or CoreSND, but it will always be assigned to only ONE CoreXL or CoreSND, as if the process really had this limitation of being single-core (perhaps an issue with Kernel 3.14 used up to version R81.20).
• When the FW has many Cores, GAiA itself seems to create a Core only for the fwd process (this is exactly about the documentation you sent, but GAiA does this automatically in the First Wizard).
The documentation you sent is to be used in the first case, where the FW has few cores and no specific core is set for the fwd. By doing the documentation, you set a core to be responsible only for the fwd process.
In a Lab (ESXi) I created a VM with 28 cores, look at the behavior in R81.20:
I did the documentation you mentioned, with the intention of adding another core for the fwd process, but it doesn't work, only one core is allowed for the fwd process. In this specific client that I mentioned, the boxes are well designed and GAiA has already automatically set a core for the fwd process. I can't put 2 cores for the fwd process, for example.
Now, look at how the R82 version turned out. No specific core was set for fwd, I believe that in the R82 version, the fwd process is now multi-threaded, this was said in the EA version of R82: