FIRESYSOK
The difference is you add it as an afterthought whereas it's the first investigative action in the procedures. It shows clearly the reason electrical equipment must be able to be electrically isolate individually and therefore addresses the original point.
When/if I have smoke in the flight deck, I'm going to know right away which system is offending? You sure about that?
I'm going far, far out on a limb here and pretty much say that unless it's clear it's a coffee maker, oven, or something not in the FD, I'm not going to have time, nor want to waste time analyzing which system it is, then waste more time considering how to do that ("where is that darn VHF3 circuit breaker again?!"). Rather, I'm going to depower busses PER THE CHECKLIST, and wait to see if smoke decreases or not. All the while running toward the ERA or nearest airport.
I suggest you follow the checklist for your type.
I have had smoke in the cockpit.
We were some way from a suitable airport.
We could identify the area the smoke was coming from and by opening a panel could identify the item.
We isolated it then removed it to a safe area.
In doing so we were able to maintain the other systems powered by the same bus.
This was according to our checklist.
All electrical smoke checklists have the same flow.
OXY/COMMS
ISOLATE THE SOURCE
IF UNABLE TO IDENTIFY THE SOURCE AND CLOSE TO A RUNWAY LAND
IF NOT CLOSE TO A RUNWAY POWER DOWN BUSBARS TO TRY AND STOP THE SMOKE.
They all are written in that priority.