Quite simply a CC looking out of the window on the RHS will not see a (small) fire which is underneath them unless it got big, quite fast. If they saw flames they would not be opening any exits. A bit of smoke is not necessarily in itself a hazard...
Keep in mind that the CC can block at any time and redirect the pax. Wouldn't be the first time an exit was opened as it seemed fine but on getting a proper look the CC would see it's not a good idea to send people down.
A lot depends on if they received specific instructions from the flight deck or not