Even those 1-10GW numbers aren't enough.
(60000000000 MJ) / (1000000000 watts) = 2 years
(69.4 days if you have 10 billion watts)
Going the other way around, releasing that energy in 0.1 seconds requires:
(60000000000 MJ) / (0.1 seconds) = 6E17 Watts
or almost 60 million times more energy than what Tesla himself claimed he could do.
Your source, Oliver Nichelson, seems to have done the wrong math (or perhaps I did?). 1 megaton of TNT is 4.184E15 J
(4.18400E15 joules) / (1 000 000 000 watts) = 48.4 days
(4.8 days if you have 10 billion watts)
48 days is not an "incomparably small interval of time". And if released in 0.1 seconds:
(4.18400E15 joules) / (0.1 s) = 4.1E16 Watts
or about 4 million times more powerful than what Tesla claimed he could do.
Also, it doesn't seem like Nichelson is clear about the difference between power and energy.
Power is the energy transferred or converted per unit time. That's why it's measured in watts = Joules/s or the equivalent in other systems.
Energy is just the Joule part of that term. The phrase 'If that amount of power were released in 'an incomparably small interval of time,' is imprecise. It should be 'that amount of energy', which would then give the needed J/s for power. But there's no reference to what that amount of energy was.
Thing is, the power supply was already given, as "tens of billions of watts". You can't release tens of billions of watts - J/s - in an incomparably small interval of time because that's meaningless - power isn't measured in J/s/s.
What you can do is release tens of billions of energy in an incomparably small interval of time. But it would take time - months or even years - to build up that energy with only a 1-10 GW power supply.
The essay you link to doesn't describe how that energy is stored before release. At best is says "build up electric fields", but it still takes days to get that much energy in the first place.
Since the math doesn't work out, since the author seems to be confused between power and energy, and since there's no explanation of how Telsa could have generated 60000000000 MJ of energy, much less release it in a split second, I think it's appropriate to discount the thesis of that essay.