i am pretty sure they arent a substitute for chins. i have carried an elbow injury for months. I stopped chins and pullups to allow the elbow to heal for a month. bicep curls seem to do not harm though because its really light weight.
Also switched to high bar squats for the same reason. Every time i did low bar squats, my elbow hurt so bad, i couldnt even do 100lb on the press. But the high bar position is allowing me to continue progressing on the other lifts.