In no way you can consider PGT-TVC with route you mentioned. Kerala is not like TN, where there are many branched. We just have one mail line. TVC-MAQ, which has branch to PGT. This main line you can compare with MAS-CBE route of TN. Then we should say that Kerala is neglected, not fully electrified, not fully doubled. Compared to number of trains plying through SRR-TVC route, CGL route has less number of train.So please don't compare these two routes.
TN is big state, vast rail n/w so it will take time for completion. Kerala is small area, so the high traffic area is doubled just like in tami nadu.