black tank chemicals

So I recently posted about leaving the black tank full while I was gone form our seasonal to help in tank digestion before I return to dump it. I received a lot of replies (on here and another forum) from folks who say these chemicals don't do anything but maybe help with odor.
Now I know you can't believe everything you read and I doubt any of these folks are scientists or have ever really tested this theory... but maybe.
So my question is, has anyone ever really tested this? These products advertise "break down solids", "enzymes digest waste", "liquefies waste" etc. etc.
Not that you'd $#!* in a jar, pour some chemicals over it and watch what it does but... there sure are a lot of companies out there promoting these chemicals so I thought I'd ask.
Maybe someone has some scientific evidence we could all learn from.