For a period of time I used glass inserts for the Epson holders. They were not Anti-Newton glass, but they had one matte surface which goes against the film. I was not at all happy with the results, I suspect the quality of the glass was not first rate. The ANR glass inserts may be better, but for me the 120 format is not the biggest problem. At least the films I use do not curl as much as 135 film. The 4mm thick, heavy glass inserts for 135 was no match for curled film, the glass was left balancing on top of the film. I've tried to put 135mm films under pressure for days, but it does not help much. You just have to wait until the built-in tension of the film subsides. The alternative is to use films with a PET base, they dry really flat. Rollei and Adox use this base in many of their films, but they are usually very thin. Despite that I have not had any problems with this type of film in any of my cameras.
There is one thing about the film holders for flat bed scanners that I think many do not pay attention to, and that is the fact that the height of these holder may need to be adjusted. The Better Scanning holders have very good adjustment possibilities. Even the Epson holders have a type of adjustment, although somewhat crude.