4seventy,
If you compare your Rizzini DR action to the Perazzi, I think you'll find that they are vastly different in design.
I'm not suggesting there is anything wrong with the Rizzini, just that it is a different action design compared to the Perazzi.

Perazzi incorporates many strengthening features in their O/U actions compared to other Italian makers.
The Perazzi DR action shown in the link is a very good design indeed for handling rifle cartridge pressures.

It features very thick bolstered sidewalls, the hinge trunnions are supported by the knuckle, axial load on firing is taken mainly by the (large) lump radius, barrel bites are integral to the monobloc, and are positioned nice and high, and locking bolts are located deep within the action frame.
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I did compare the two actions, and I fail to see "vastly different design" you speak about. What I do see is vastly similar disign, with only minor differences.

Perazzi does, indeed, incorporate strengthening features in their o/U action, but so does Rizzini!

You say the Perazzi "features very thick bolstered sidewalls," (So DOES THE RIZZINI) the hinge trunnions are supported by the knuckle (SO IS THE RIZZINI), axial load on firing is taken mainly by the large lump radius (SO IS THE RIZZINI, AND RIZZINI HAS TWO LARGE BARREL LUMPS EXTENDING DOWN THROUGH THE ACTION FRAME THAT TAKE CONSIDERABLE FIRING STRESS, barrel bites are integral to the monobloc, and are positioned nice and high (SAME AS RIZZINI), and locking bolts are located deep within the action frame (SAME AS RIZZINI).
As I said, the majority of Italian O/U actions today, are built on same basic action type, varying only in insignificant ways.