Not so fast, there.
In low-level play I've no way of knowing which characters will still be in play in the next hour, never mind next session.
And later, the players are likely to have multiple characters each; and I've no way of knowing which one(s) each will bring on any given mission or adventure.
So no, oftentimes I don't know what characters will be in play when any given circumstance is reached.
I'm going to go out on a limb here and say that you're table's a teeny, tiny bit of an outlier though.
Basically, your advice only really works if I play troupe play with high lethality and extended campaigns that last multiple years. Since none of that is true for my table (and I've a sneaking suspicion that it's not true for most tables) I'm not really sure your opinion here is particularly pertinent.
Honestly though, I think there is room for both. Sometimes, it's great to sit back and let the players do their thing. Here's a bunch of options, with the potential for choosing something that isn't on the menu, go to it. And, sometimes it's great to start in medias res, halfway into the action, and hit things at a dead run.
And, it's going to depend a lot on the adventure. Earlier, a mystery was mentioned. Well, think about that for a second. Most of the time, the DM is going to know who did what to whom and where. They have the answer to the mystery and it's up to the players to reveal it. From an adventure design standpoint, there's not a whole lot of freedom to choose here. You're either right or you're wrong. Follow the clues, find the killer, catch the killer.
Now, granted, I know there are games out there that make the answer somewhat nebulous and the DM actually doesn't have the answers at the outset. But, by and large, If Colonel Mustard offed Mr. Green in the Study with the Lead Pipe, well, that's the end point of your story. You follow the clues, catch Colonel Mustard. Or fail to catch him as the case may be. But, in any case, the structure of that adventure is going to be pretty fixed - find the clues (maybe using the 3 clue method), follow the trail of breadcrumbs, climactic ending. Story done.
It's going to depend really heavily on the needs of the adventure really. You can't have an emergent mystery story. Well, actually there are systems where you can, but, in D&D? No. You can't. The DM knows whodunnit before the first player sits down.l