I managed to troubleshoot this issue even further today to find out that this could specifically be a bug for the uncomfortable (exhausted) mood.
I had no problem killing my sim through starvation. However, if I have him with exhausted (pass out in...) alongside ravenous (die from starvation...) my Sim doesn’t die from drowning or hunger. The Sim doesn’t starve to death when put on land or passes out at all. If I fill my energy need all the way to full and still have the uncomfortable (ravenous) mood, the Sim will not starve to death.
I had to reset the Sim to remove the uncomfortable mood, then he/she can eventually die from starvation.
The Sim can successfully pass out on the floor if the ravenous moodlet isn’t down to 0 (starve to death). As long as I don’t have my Sim exhausted (pass out in 0) while in the pool, death from starvation works and passing out on the floor works.