Of course. If you want to use autotune, you need to insert it on invidual channels. Not on a group of “untuned” separate voices. Autotune can’t handle that.
Same with compression or eq, if you need to correct one of the voices or multiple voices in a different way do it on the channel before the group.
Maybe it is elpful for you to notice that GROUP-channels are by nature SUMMING-Channels and linking parameters of individual channels and the VCA-Faders are for “grouping” multiple individual channels without summing.