Just repeating what DV has stated. He has extensive experience in the high performance industry. Others have broken SBF blocks also. Now if you watched the DV video, he states he has not broken many blocks, but all were over 500HP. I like the Fords myself for their compact design. DV also states the older blocks, production line, are stronger. The FRPP blocks are stronger and heavier than production line blocks.
Now if you are going to build a 550 to 600HP small block, that is going to require an expenditure of hard earned cash. By the time you pay for machining, forged rods, pistons, possibly crank, cam and valvetrain and heads whether porting factory or aftermarket, your wallet is going to be lighter. To me a little insurance to help prevent a failure that ruins a good chunk of those expensive parts is probably well advised.