The modification to the QRH was for the reason that Wingswinger says, since the sequential electrical shedding
for diagnosing/eliminating the source of the smoke had the potential to cause problems. However, this is not the reason for that line in the QRH, which tells you to disregard the instruction to reset the GENs if the ECAM smoke warning was not triggered.
Even if the avionics smoke warning had been triggerred why would you want to try a gen reset
The direction to disregard the GEN RESET warning is still present in the QRH, though, as WS quotes.
Let's consider that all our attempts at eliminating the suspected electrical smoke source have failed, and things are getting serious. We might decide to enter EMER ELEC config to shed all non-essential electrical loads.
If the ECAM AVIONICS SMOKE warning was triggered, the ECAM
knows not to tell to reset the generators after entering EMER ELEC config. If
you elect to enter EMER ELEC yourself, the ECAM doesn't know this and 'sees' the entry into EMER ELEC CONFIG as the problem, not the solution, so it will tell you to try a GEN RESET.
So you are right, you
wouldn't want to reset the GENs if you deliberately entered EMER ELEC CONFIG. If the ECAM AVNCS SMOKE warning
was triggered, the ECAM wouldn't mention anything about a gen reset.