I agree with your first reason, except I'd expand it to you should have the chance for a comeback even in a double elimination portion of a tournament.
For your second reason, I think a run rule helps the winning team more? A losing team can always put their shittiest pitching out there if they are going to give up. The run rule would be better for them, but not by a huge margin. For the winning team, it's always a risk to try to close out a game with worse pitchers to try to save pitchers for the next game. The run rule means they can shut it down and not have to worry about who they are putting out there.
But regardless, agree on now run rule in the post season for baseball. It's the post season. Play the full game.
On the 2nd reason, I kinda disagree. Unless its the final game of the regional, super regional, or CWS, the run rule helps the losing team way more. Note: this applies strictly to baseball.
If a big lead has been built by one team, it means both of 2 things have happened:
-Team A has been unable to score much on Team B
-Team A had been unable to stop Team B from scoring.
In your scenario where Team A can just use their worst pitching to “give up” that particular game, I contend that it’s actually the opposite. Team B has built the big lead in part due to strong starting pitching. That starter isn’t coming back until the following weekend regardless, so they can leave him out there longer to just pump strikes, and then bring in their back end guys to clean up whatever is left just by throwing strikes and letting the law of averages take over from there. All the while, Team A, at some point, has to stop Team B from scoring. Whether you have good pitching or bad, it’s infinitely easier to pitch with a big lead than in a tight game or with a big deficit. Having the luxury of being able to allow hits and runs at a moderate pace is something that only ever happens for a team winning in a blowout.
But regardless…..say I’m wrong and you’re right….or maybe we’re both right in certain ways. I still disagree on principle that a team should get any advantage that goes beyond the specific game in question by being allowed the gift of an early blowout win. Say it’s a winner’s bracket game where the 2-seed had to record 33 outs to win in extra innings, and the 1-seed only had to record 21 outs to blowout their 4-seed. It puts one team at a profound disadvantage from the onset.
None of this really applies to softball. I can kind of see the purpose for run rule there, because pitchers have near infinite use and don’t have the arm wear-and-tear of baseball, so its not near as much of an advantage / disadvantage either way.