A Mistake by GA

[Kor]

The fact is that doors like that exist. Whether or not it seems logical is another thing, but it's definitely not a mistake.

[Watson]

On the train in might make some sense, as the compartments have limited space.  A door opening into the compartment would limit the space further.

It would be unlikely for a hotel, however, as it poses a security and safety issue.  It's still a matter of how the rooms ate laid out, though.  There could be something that makes it more practical for the doors to open out.

In the bell tree train, it was said that when opening the door it could cover most of the corridor (this was needed for the mirror trick) so if the corridor is that tiny, it wouldn't make sense to make the door open to the outside.

If it opened into the compartment it would hit anyone sitting beside the door.

That chances of you hitting someone sitting on a tiny corridor is far greater

You are suggesting that it is more likely for people to be in the corridor than in their compartment?