I actually made an account just so I can comment on this. I witnessed the "no voice" issue as well, but only when I played one of the Wretches and Riches dlc, when I supported Lukas and Python on the map.
Afterwards however, I went to check the support log and when i replayed their support, it played with voices.
I tried their support again on another file but on a normal map battle and the voices were there. So maybe it's just a dlc issue.