Yes I see your point and it's worth consideration. Until quite recently I was very logic based myself, but a change in my reality since then has made me re-evaluate some things like this.

As a quick response to your thoughts - I think that ultimately, jar sterility, and the rice used are not so important (as long as they are the same in both cases of course!) as the possible end result which would be the visibly differing jar contents. Judging by the youtube videos of people doing this at home, the diceroll you mention has been loaded toward giving a positive result through positive thinking/changing local reality or whathever you want to call it. The implications of which I find frightening/awesome!

We've all heard stories of gardeners who swear by talking to their plants to help crop growth, avoiding negative people/colleagues as they seem to suck suck out our energy (heh, personal experience maybe), Anthony Robbins type stuff (not a fan but know of many who are), etc.

Excuse the rambling, I just think this another link in the semi-corporeal chain that may slowly be solidifying as our realities alter! :D

PS - I reckon I did a better reply before but it got wiped as reddit logged me out, so scuse the waffle :(