I do not dispute that rimmed cases can get expanded primer pockets. I personally have never owned a high pressure rimmed case such as a 220 Swift, a 225 Winchester, 356 Winchester, but I would think you can could generate enough pressure to expand a primer pocket. I have gotten sloppy primer pockets with 22 Hornets that were over loaded, so I know it is possible to have rimmed cases get loose primer pockets.
All cases can fail right above the web. This is due to the case stretching in this area until it fails. This usually happens after several re-loadings, but if there is enough head space and high enough pressure, they could fail on a first or second loading. Most of the case stretch happens in this area.
I would think if a case fails in the extraction groove, it would have to be a defect in the case. There is lots of brass in this area, even in a rimless case so it should fail some where else before failing in the groove. Look at a cross section of a case and you can see that there is a lot of brass in this area.
If a rimless case can take so much pressure, then a rimmed case of identical design will handle pressure in the head area just a little bit better, due to the extra ring of brass in the same plane of primer pocket expansion. It would be like putting a tight washer over the end of a pipe. It will handle more pressure here with the washer than with out it, just how much more? How much, I do not know, but it will take a little more, due to the extra mass/reenforcement in the same area. It is sort of a moot point however because if the rimless case is so high of pressure it causes the primer pocket to expand, then you are asking for trouble even with a rimmed case. The bottom line - if the rimless case will handle 60K psi, then a rimmed case of identical design will surely handle it as well.
Good Luck and Good Shooting