Nice to hear back from you!
The application example shown in the datasheet is for WIDTH EXPANSION that is why it has common select lines.
For example, you can get x72 data bus width by using two x36 devices with this setup.
But if we would like to go for DEPTH EXPANSION then of course, we need to have different selection lines (read/write) for each memory to select one of them.
Yes, that makes complete sense, thank you!