Why can't a user connect via SFTP to a directory on which he has write permissions?

Question

System administration

Good day.
Prompt, please, in what there can be a business.
Created a user, limited him access via SFTP to a single directory. Connects fine, but can't record anything. If I grant write permissions, the connection is impossible. If I restrict the directory above, while saving write permissions to the directory inside, then everything is fine.

Answer 1

Because writing to a directory is also changing the table of contents element of the directory itself, which is included in the top-level directory, writing to which is prohibited :)