@User: There is a rule

spacing pc allpdifflv,allpdiffmv 235 touching_illegal \
        "poly contact spacing to P-diffusion < %d (licon.9 + psdm.5a)"

However, there was a typo that I found a couple of days ago that effectively caused a block of DRC rules to be completely ignored, and I think that was among them. I patched that error in open_pdks either yesterday or the day before.