I might have to disagree with your response. The difference might be in how the job is done and by whom.

In '75 I took a H&H Royal ejector, H&H mounted Ajack 'scope that had been converted by them from .300 flanged Mag to . 300 H&H Belted. I could still use the flanged cartridge in it and I did. The converted ejectors seemed to work fine and never failed at the range. However, since I had a lot of brass I took the flanged on the trip.

With the flanged brass it does leave the area of the belt unsupported, but most if not all of that area is solid. I never experienced any problem in the 10 years or so I had the rifle.