Is it the country of your registration that matters for the multiplication or the country itself? For example, will everyone receive 4.5 points per Real for domestic flights in Brazil, or just Brazilian residents, and Peruvians will get 22.5 for Brazilian domestic flights?

It only applies to citizens or permanent residents. I assume that the huge difference in qualifying points earned in every country is to be more competitive in markets where LATAM isn't the top dog. In Colombia, for instance, they compete hard against Avianca. So making it easy to achieve the top categories might be attractive for local flyers. On top of that, due to Colombia�s geography and poor road infrastructure, Colombians prefer to fly from one city to another.
The competition in Brazil is huge as well.

On the other hand, like Chile, i.e., LATAM dominates the market by far and has massive contracts with mining companies. They don't need to lower the bar for flyers to achieve top tiers categories in order to be chosen.

At the end of the day, (like every business), everything comes down to profit and make money more than anything else.

It�s the country you fly in. As a US member I get the current 12 points per USD on national flights in Colombia. I haven�t flown nationally in PE or BR yet so can�t verify. Assuming next year will be the same, I would get 30 points for Full and PE fares.

So all the reason why they should use fare class as a priority factor. Why should someone on a plus fare get upgraded over a full fare ticket just because they were faster at requesting an upgrade.

For now Latam is not part of any alliance like they were before in One World but they will have to one day to be competitive so I expect this change to align with other airlines when it does happen.