Mixpanel Session Replay Issue with Rudderstack Integration

I'm using Mixpanel with Rudderstack. For session replays, all recordings are capturing against an ID like this: $device:uuid Instead of just uuid. This means they're not getting stitched together with the anonymous_id from Rudderstack. We've just used the code directly off the Mixpanel docs, so just wanted to check what we were missing. I can see it manually appends $device: - will there be any issues if I stop appending this? Thanks!