This is a very technical question; possibly a Rogers engineer could shed some light on this.
I just bought a Samsung S20 Ultra, and I am troubleshooting poor audio (drop-outs) with WiFi calling. I took a packet capture of what the WiFi calling looks like, and it is an IPSec tunnel; presumably it's RTP inside.
Inbound DSCP (for QoS) is set to AF22 (medium) and outbound is CS0 (none). I believe setting the DSCP to EF (high priority) would give better WiFi calling performance. It would indicate to networking gear in between that the packets should be queued for as little time as possible.
I use VOIP on my network as well (Callcentric), which sets DSCP to EF, and the call quality is MUCH better than Rogers WiFi calling, at least on my phone.