Possibly the case is that the Petrification effect is just listed, while blind beings are only immune to blindness/eye loss. I don't think it can be changed outside of mayor code reworking...
As for undead - skeletons should probably get "blind" feature, as are probably those whose description says they are using some kind of "lifesense" instead of normal vision. And they surely can be petrified - except those ethereal who probably have nothing that can be turned to stone! I don't know whether such change is planned & how it looks from balance point of view (but it also would require re-coding)...