What you have stated is entirely true. However, there are also contentions that at least in Kenya, Meta violated Kenyan labour laws in its use of a content moderation firm. Meta tried to claim rather unsuccessfully that they shouldn't be bound by Kenyan laws since they aren't based in Kenya. This can be found here and here, I think it is slightly indicative that the use of outsourcing companies is an aim to limit their liability in jurisdictions outside of the US. The case hasn't been concluded since it has been sent to mediation. It is what raised this question in the first place.

You're 100% correct. It is data labelling (an oversight on my part)

I'll try to avoid stating anything that has been discussed in other comments and this will be fairly brief. I have a few intuitive problems with the paper:

1. It narrows the impact of risk to that of an existential level. As has been stated even within the comments the number of deaths and suffering that would be caused is a reason to treat it as a priority. Even within EA most of its funding is channelled towards global health and development, and most if not all of these causes do not pose existential risk.
2. One of the reasons that climate change is targeted as a cause area is that it is extremely tractable. By this I mean, that the decades of research has given us means to reduce emissions and the impact of climate change. While this may not be the case for unaligned AI and engineered pandemics which do not have a clear or easy to implement solution.
3. Merely because the primary effect (temperature increase) would not cause existential level risk, does not mean we know of all of the secondary effects on humanity. The ecological collapse of many ecosystems could greatly negatively impact or our access to food sources. Most of the world’s food supply is partially produced in the tropics because of extremely fertile lands which may be difficult to replicate or replace.
4. Even outside of human reasons to prevent climate change, it would be devastating for various flora and fauna. A lot of which would be unable to adapt to such a stark temperature increase in a short period of time. It would be extremely bad for non-human animals if it were deprioritised.