When I flew IPC-SCL-(LIM-)LAX I had to clear customs at SCL as a domestic pax, and then go back through immigration to get airside for my onward flight.

But EZE-SCL-IPC I was able to avoid immigration and stay airside*. AFAIK it depends on whether the international transit is open or not.

* note this caused me a problem at IPC as I failed to enter Chile at SCL I self-declared I needed to enter the country. If I'd kept my mouth shut I probably would have had an issue at SCL on the way back for not legally entering the country.