I personally do not like the metal frame rests. I snag the nails when scraping and I "feel" mold, virus and bacteria "can" hide out behind them.
I made some Cedar hive boxes which are very soft, ones skills necessarily get better. I run the edge of the tool 90 Degrees to the surface, "paint scrapper" way and gouging is less than, when trying to slice the propolis off. Also I normally have a torch and "warm" the area scrapping is easier them, I use the propolis stuck on the tool as putty to fix holes and cracks, which IMO is what the gooey stuff is for anyway. Buy the way all of it need not be removed ,just smooth a bit and get the big chunks off. However if you feel the metal frame rests help you they are cheap. I guess it is personal preference. I never had any the first 15 years so I got used to not having them there. Later I obtained some used boxes with them on and did not care for them enough to add any to my other boxes.
GG