I've noticed similar seed size variation. Neville's haze has fairly small seeds. Seed from Thailand and Cambodia that I have collected was mostly larger. In my view larger seed size is a preferable trait. Large calyxes produce large seed. I prefer to select for large calyxes. It seems to help increase the calyx to leaf ratio.
i have some seeds that an outdoor plant gave me. i assume it produced seeds due to my neighbors motion light behind us going on and off all night. i grow it (blue dream) every year from these seeds and never had a problem. my indoor room had a light leak so the one time i grew it there it hermied. now do hermie seeds look different?? im assuming my seeds didnt keep the hermie trait because i havent had that problem since the light leak. anywho heres a pic of my sativa seeds (from the outdoor grow) and a indica strain i called monster because of the colas i got the first year. theyre similar in size