I've developed Efke 25 in 120 format using stainless steel reels and haven't had a problem with any residue on the film, so I know this isn't an "every time" problem. I do pre-soak everything (usually 1 minute with 10 seconds of gentle agitation to start and 10 more after 30 seconds).
After reading as much as I could on film production, I thought all old-style B&W films had a thin gelatine coating to protect the emulsion. Regardless of whether they do or do not, I'd think any coating on the front or back of the film would be washed away with either a quick soak or with the liquid in the developer.
If the sticky stuff is on the short side of the film, my money's on the glue from the tape that holds the film to the backing. (I know that I found this tape a little harder to remove on the Efke films than on most.) If it's on the long side of the film, then my suspicion definately leans toward something on the reels. If you're using stainless steel reels, just soak them in very hot water for a little while and dry them thoroughly before you use them again.
The pictures to which you posted links are gorgeous. Obviously this is a film you can work with and get great results. I hope you find a way to deal with this residue problem.