I wonder if the BHP knows that being that the cast frame is widely accepted as being stronger.
That statement, that casting is stronger than forging, has so many unknowns it can't possibly be a true or false statement all the time. It is similar to the analogy of stating that the Chevy 1500 pickup is faster than a Ford F150 pickup. Too many unknows to make any conclusive arguments either way. There are many different 1500's and many different F150's which are we comparing and in what setting?
Investment casting (as Ruger is known for) vs forging (cold or hot) both serve that same purpose for a gun maker. Getting a lump of steel (or other metal) into a near net shape part quickly and cheaply to minimize the amount of machining and other operations required to make it a finished part.
Casting can get a parts closer to final shape in more applications than forging can. Forging is typically faster and often cheaper and with cold forging the forging results in a stronger raw part (compared to a casting of the same alloy) due to residual stressed and work hardening of the material. Sometimes this residual work hardening is sufficient for the parts application and no heat treat is required post forging. In the gun industry this is uncommon with steel parts. Casting, if not done right, can introduce flaws in the metal, voids, porosity and even alloying element separation in extreme cases. Forging tends to eliminate or at least reduce micro flaws and voids in the original billet of material during the forging process.
In most cases cast or forged parts are normalize after the casting or forging process. Normalizing eliminates internal stresses from the forging or freezing (with cast) process and helps keeps parts from warping during the machining step. Then machined to final shape. Then heat treated (quenched and tempered, austemper, etc) to achieve the desired hardness to give the needed strength or toughness to the part. So ultimately if we start with the same exact alloy, cast and forge them to the same net shape, normalize them the same, machine them to the same final shape, heat treat them the same. It will be hard to tell the difference between the two parts. They will have nearly identical mechanical properties.
That said some alloys cast better than forge and vice versa. There is a huge number of variables to selecting the alloy, process to get to near-net and final shape and the heat treating processes applied.
TL; DR: The blanket statement that casting is better or worst than forging cannot be sustain as factual.