Not Necessarily TRUE. However .....
There are some "Old Wives Tales" that just refuse to die. Or even just go away.
I am always amazed at the BP shooters whom are frantically searching for their jug of soapy water to immediately immerse their obviously contaminated cartridge cases in. Most of the time I just chuckle quietly as I walk by.
Some times it days before I clean my BP and Subs cases. A. I'm lazy and B. I forget. Regardless, at a match I just toss my brass in my cartridge bag and don't worry about it. It's not about to suddenly dissolve. After I get home (next day - next week) I dump my brass inna sink with warm water and fair amount of WHITE VINEGAR. Soak for half our. Rinse. Dry. Tumble for about an hour (unless I forget).
Where was I ......... Oh yea......
Don't panic if your not diligent with your fired cases. Not gonna dissolve. May not look pretty, but their just fine.
Oh yea, and I also suggest if your shooting a Toggle Link rifle with a Brass Carrier Block, Pull the carrier block and put it in to soak with the brass. Tumble it too. Just don't use smokeless solvents on it first.
Coffinmaker