science

The questions I pose are to understand whether what is saying is actually a threat or just some scaremongering.

Well, only if it scares you 😉.

But seriously, I don't think It's really anything to worry about. It was pointed out that other forms of energy generation, like wind or tidal, or hydroelectric can have this same effect of slowing planetary rotation (Hydroelectric has actually had measurable effects on the rotational velocity, there were studies). Likewise, geothermal power accelerates core cooling (nominally). Which ultimately could also mean our demise. So we don't really have better options.

But all of this is so long term, none of it would matter for hundreds of thousands of generations of humans. And to be quite honest, I will assert right now that in hundreds of thousands of generations, the human race will have both different means of power generation and different planets to live on. (Or we won't still be around and it's all moot.)

So no, no reason for anyone to worry about this, maybe ever.