Pinch hitters. Some pro-games allow them and others don't. All pro games of baseball are not the same. You get more and more rules changes as you go down towards little league.
Major league fields vary in size.
What's more, there are many different offensive and defensive strategies, methods for hitting, etc. that are not bound by the rules, but which do drastically influence how the games play. A baseball game is much more than just the rules.
Ok, this is swimming a bit far upfield. And, against my better judgement, I'll try this out.
Note, in the quote you quoted, there is the following line:
"You can follow the steps exactly as written down and EVERY game of baseball
(presuming they are playing from the same rulebook) will follow exactly the same steps."
Now, all your examples of different games playing differently because they have different rule books is pretty much moot because, well, I already account for that.
And, you are still missing the point. In order to play a baseball game, or nearly any game, all you do is follow the rules. Start at rule 1, end at rule X and play until the pre-defined win conditions are met. EVERY SINGLE GAME will play the same so long as you are using the same rules. Yes, this team or that team will win. Fair enough. But, the start point and end point will always, always be the same.
At no point in a baseball game can I remove second base. Or choose not to pitch. Or, in fact, do anything not specifically allowed by the rules of the game. The rules of the game are
prescriptive.
The rules in an RPG are not prescriptive. They are descriptive. They tell you how to resolve certain actions from the players, but, are certainly not meant as an exhaustive list of every action the player can take. In fact, the rules of an RPG specifically state that they cannot provide an exhaustive list, and thus, are meant as guidelines for the players to use in determining the outcomes of actions.
Put it this way. There are no rules for jumping in AD&D 1e. None. The rules are 100% silent on how far or high a character may jump. Now, in a non-rpg this would mean that jumping was not allowed. You cannot jump in Monopoly. You cannot jump in Catan. While you can jump in baseball, you can only do so at certain times - you cannot jump while pitching for example. But, despite not having any rules for jumping in AD&D, characters most certainly can jump and are often expected to do so.
Thus, we get a range of possible adjudications for jumping in AD&D 1e. From "You jump this far" to "Make a save vs X to jump this far". to whatever else people come up with.
You cannot sit down, read the rule books of an RPG and just start playing. It doesn't work. You need to do a fair bit more work first - choose/create a setting (which is not defined by the rules), choose characters (partially defined by the rules), choose what you are going to do in that setting (certainly not defined by the rules).
Does this make it clearer?