Yea, I know nothing about the +1 thing and how to actually get that for mentor... This being said, I could see this happening... It is in fact if thats THE ONLY way to get +1 stone from mentor, then this is true, though I don't know if anyone could have it identified... When I randomly plvl noobs or make a water (rarely)... I notice on my archer, I'm getting my mentor +1 stone... I thought to myself, how is this possible, I haven't or will ever do ANYTHING with my archer, just plvl...
So yea, I sure as heck don't know how to do it, but there could be a way.