Slip Cases For Minkus Global Albums

I just purchased an old Minkus Slip Case for my one of my Minkus Global Supreme albums. When I tried to use it I discovered that my "new" old slip cover is 1/4" too short.

Is the difference relating to the old curved back Minkus binders as opposed to the newer flat back binders? Were they different heights? I use old curved back binders for my collection. I suspect that the newer flat back binders may be shorter. Anyone else run into this?

I do not have any Minkus slip cases but I do have both flat and curved albums. The newer flat albums are 11 11/16" tall and 10 5/16" deep, the curved back albums are 11 7/8" tall and 9 5/8" deep.

Older, curved back Minkus binders = 11 14/16" tall. (Slightly taller)
Newer, flat back Minkus binders = 11 11/16" tall. (Slightly shorter)
(Using Eric99's measurements, not my own)

If the older (curved spine) binders were taller (11 14/16") than the newer flat binders (11 11/16"), why would an older slipcase that fit the older, taller binders not fit both the older and newer binders? I'm confused.