As documented, this is a limitation of how changing of properties is implemented for SCP protocol:
https://winscp.net/eng/docs/ui_permissions#other_options

Use SFTP, if you want different behavior.

SCP,Server CentOS6.

I have to execute the command in A directory:
find -type d -print0 | xargs -0 chmod 755
to correct it.
The directories in A directory only have 644 before even I've chosen "Add X to directories" when I edit A directory's property.
(Recursively chosed)