Nope. It's maybe not good advice, but it is correct. The steel framed Italian bp revolvers can all safely handle a full chamber of real black powder. They are all proof tested before shipment.
Now, understand that the full chamber will be about the most inaccurate load you can shoot; a goodly percentage of the powder will be expelled and burned outside the gun (hence lots of smoke and flame and fun), and another goodly percentage will fall to the ground out in front of the gun unburned. But, it will be fun, and lots of people do it.
You can also use a full chamber of the substitute powders if you'd rather, although you dont' get the same smoke/flame effect. And accuracy will likely be even worse.
Oh, and I use 22 gr 777 or 25 gr Goex in my Pietta and Euroarms 1860's.