Square corners on hardcover book

I'm pretty sure it used to be that the hardcover book (the non-round corners version) had square corners on the foredge side, but just noticed that they now have a slight rounding to them.

Although this may well be a perfectly good shape for many people, the hardcover books we produce all have square corners, without rounding.

Would it be possible to have a variation, either as a new shape or a control within the hardcover book shape settings?