The second best thing to do is usually still a pretty good thing to do. Don't punish players because they didn't happen to come up with the one way to defeat your Big Bad Evil Villain that you had planned out. Stories never work out that way.
Commentary by memnarch (who has not seen the movie)
Of course there can't be any other reason. That would just be silly. The red lights on the railings look really weird in screencap, though, I have to say. The area is reasonably lit with actual light, but they all still have a solid red to pink hue. Seriously; the saturation is like 99-100%! Previously the harsh First Order red lighting felt a bit odd, but it fit with the gloomy environment, skin coloring problem aside. If the lights here look like this in the movie as well, this scene must feel unsettling with them standing out so much.
And of course they split up. It was foretold after all. But if Han is going away from the rest of the protagonist characters and heading downwards, maybe he's not going to die that soon? It would feel really odd to have him die where none of the other Team Good Guy characters (or Finn) see it happen. We'd miss out on a callback to one of the most meaningful parts of the original movie!
(No Name): The railings must be a clue.
Chewbacca: Well, there certainly couldn’t be any other reason for them to be here.
(No Name): Right! They clearly indicate this place is super important. They mustn’t want anything falling down there.
(No Name): We’ll plant the explosives and send tons of debris crashing down.
Chewbacca: I must admit I have no superior suggestion in our present circumstance.
(No Name): Great! You take the upper levels, I’ll go down there. Meet back here.
Chewbacca: We’re splitting up?
(No Name): You got a better idea?
Chewbacca: Just one.
(No Name): So splitting up is very close to the best thing we can do!
Chewbacca: <sigh> Can I take the detonator?
(No Name): If it makes you feel any better.
Chewbacca: Safer, at any rate.