You can look at it like that. I’m looking at it from the point of view of what makes the game more fun. If I take your baking a cake analogy, do you read the recipe before shopping for ingredients? The current turn order is basically, buy some ingredients, read the recipe (combat movement), bake cake (conduct combat). You have to prognosticate what will be in the recipe to know what you need to buy.
No combat movement would be moving all of your ingredients to stove. 😉
I think my analogy is every bit as valid as yours.
The point is that the need to prognosticate the likely outcome of the board at the end of your combats is unnecessary, time consuming and reduces the fun. Whether the current rule makes sense or not isn’t really relevant.
The point about forgetting to purchase isn’t really valid with a Triple-A game because it prompts you. You can say that a forgotten purchase is a zero purchase if you apply the rule strictly. In general I would expect so if a retrospective purchase gives an unfair advantage.
Face to face, I use a merged purchase+combat movement phase. Probably why we can play a game in a day.