And not just the PDP-10. I think just about every DEC computer had a version of TECO, right?
Very likely. There were a lot of implementations, but it had grown in size, that address space was an issue. I do have memories of a simple TECO for RT-11, but the EMACS macros did not load/could not run (I've forgotten why). VAX/VMS eventually had a TECO which best I can tell, begat EDT, but that was after my time.
BTW: I remembered the name of the line editor for the PDP-10 I had learned before I used TECO: SOS - Son of Stopgap (I want to say the name of the IBM/TSS text editor was REDIT, but that's probably wrong). I do remember that going from the IBM system editor to SOS was very easy, the commands were similar. And, a flavor of SOS also ran on VAX/VMS before TECO or EDT arrived. As I had to relearn it, when we worked on the first VAX, since SOS was the only editor. But by that time, I had learned ed (1) and the UNIX tools and had mostly migrated away from the PDP-10. I remember being annoyed because I wanted to use regular expressions on the VAX editor, and had come to realize how much of the UNIX tool kit had become accustomed in my workflow.
Clem