No, by “separate /usr” I people who have a /usr that’s not located on the same partition as / itself. So, this: “/ and /usr are on the same partition”.

And, no, you can’t just move things around like that. You should increase the size of your / partition and move /usr back onto it or use an initramfs as described. Unless you have a simple way to make / larger, you should probably use dracut.