To be fair, it could simply mean an exoplanet, a planet outside of our solar system. I suppose "alien planet" is more intuitive than "exoplanet."

We've grown quite accustomed to the planets in our backyard, so I think the word alien is quite evocative here. I was born about 2 decades after the first moon landing, but the first confirmed exoplanets weren't discovered until my lifetime. That's pretty fricking amazing to me.

'Planet temperature' doesn't completely rule out the possibility of life. Venus for example is hot as hell on the surface but there is actually a band of the atmosphere which humans could hangout unprotected in, its breathable, the pressure is about what it is on Earth, etc. There have been some attempts to send a probe to hang out there and look for bacterial life but I don't think any have been funded.

Similarly, it might turn out that our understanding of electricity is wrong and it's really faeries playing tricks on us. But we have no evidence of faeries, so that is not a good explanation of electromagnetism.

Not true. In biochemsitry, some important compounds (eg, proteins) begin to de-nature at ~105 degrees F. So, temprature is a legitimate variable to consider, and the range between denatured protein and frozen water is not that big in Absolute scale. And (even) if you eliminate protein, you still have to deal with the properties of water (anothe ~+100ish F leway before it boils; as noted by other commenters).

You rightly note that there are examples of life (even on earth) which are in some unbelievably hostile environments (think: marianna trench) that are ungodly in temp, pressure, and ambient energy. But the absolute schema it seems more likely that these are evolved special cases of carbon-based life than the origin variants.

Som from Abslote zero to vulcanism (the possible ranges) narrowing down to 0 to 50c or 0 to 100c puts you in the right order of magnitude. At the scale of the cosmos, this seems to make some sense. Although, undeoubtedly imperfect.