Yeah and it works really well to make one shots feel more open.
You can give the players a number of locations to hunt for clues, knowing that they will always find what they need.

I completely agree with you. The idea shouldn't be 'here's a thing you have to do regardless of your choices.
It should be, 'here's a challenge on whatever path you take, but your choices alter your approach to it.'
It also needs to make sense wherever it lands, or adapt accordingly.

I think it's okay if the party get some agency in the decision. If their choices affect the nature or challenges of the battle, or it can be avoided altogether, then it's not a railroad.

Lovely formula!

I would include half feats in that debate.