Did you delete the version you copied to the USB? You want to copy the SYSTEM file to a USB Drive or Cloud Storage, and the delete the system file you copied from which is located in the System Storage (not the one you made on the USB Drive/Cloud)
I followed the instructions, (sorry for my late night babble typed from my PSvita)
First turning on my PS4, and logging into my user account.
Once I selected the settings menu on the top bar to the right. then entered the sub folder for data management. ( a much better data management system then on the Vita by a million miles.) Quickly located Terraria in the Saved Data on Syetem menu selected copy to USB, and selected and copied only the SYSTEM (misc) file.
Once the file was copied, I selected the option to delete the SYSTEM (misc) file from my PS4 Hard Drive.
After that I exited the system menu, and immediately opened the application to start Terraria back up.
Once the game started, the new colorful banner popped up, then the 505 Games logo, then the Pipeworks logo. (as intended)
The next thing that happened is the menu background loading screen appeared and a "Loading xx%" is displayed on screen. once the xx slowly climbed to 100, the normal main menu appears and I selected one of the two characters, to get to the World select menu. At this point only 1 world shows up on the menu as an option, the new world that I created yesterday.
This morning, I repeated the above steps, just in case I missed something, (only skipping the copy to USB step) and I can confirm that the results are still the same.