These newer brass companies (alpha, adg) are making their heads much harder than the older companies do (Hornady, Winchester, etc) and the fat bodied magnums (saum, wsm, prc) are maybe a bit more popular now. The harder and fatter heads are supposedly harder to size that web area with the design used in "traditional" dies.
You CAN get custom Hornady dies made that will size that area just as a micron, SAC, or Cortina die will but you'd very likely have to call and spec the die out. Alex Wheeler has mentioned many times that he likes Hornady custom dies because they work well and they will actually make them to the specs he requests, i.e. the prcW chamber and Hornady sizing die.
Here's some measurements with the EC mandrel die. When I used it after the FL die it moved the shoulder forward by 0.001 because I moved a LOT of brass in the web. You likely won't see any change from the mandrel die if you use it every time, so long as your loads aren't so stupid hot you're blowing the web out 0.003 each firing.
This is a fired unsized case. That bright line is right around 0.270... it's where the solid head transitions to the wall and is the fattest part of my case because the chamber was cut too big. It measures 0.5025 and 0.503 on some cases. The head right above extractor groove (close to 0.200 line) measures 0.500. my regular FL sizing die was also cut too big and doesn't touch the case below that bright line at 0.270. This causes me sticky extraction, similar to clickers, even with mild loads because my regular FL die won't size that tough 0.270 area down enough. It will only get it down to about 0.502.
Here's a case I used the EC mandrel die on. It now measures 0.4995+ at that 0.270 area and 0.4995- at the 0.200 line. I haven't shot any after using the mandrel die yet because I'm getting the chamber fixed and a new FL die made, but I'm 100% confident I can put a hot load in there and won't have any extraction issues. It's very close to virgin dimensions (0.499) at the 0.200 line now. Earlier in the case's life, I could put a load in there that was way too high on pressure and not have an extraction issue, even though that's not what I typically shot. I kept the pressure on the warm side but not crazy. That former was just for pressure testing. The reason I started having the problem was because of multiple reload cycles where my die wasn't sizing that portion enough... It eventually grew too large and won't give enough clearance for a loaded round.
