Earlier quoted context omitted.
I think the factor you're missing is that the WiFi and 5G connections may have substantially different latencies to the other person. Going from a lower-latency to a higher-latency connection will always involve audio dropping out and video pausing. And in the opposite direction, it's preferable to skip over a few frames in order to reduce latency, rather than maintain higher latency. I wonder if you don't see this w…
Video conferencing has latency in the 300ms - 1000ms range[1]. The actual network component of that is pretty small. And video conferencing software already has logic for time stretching/compression to handle variable latency - typically they'll speed up or slow down gaps between words and sentences. [1]: https://www.mdpi.com/2076-3417/12/24/12884
But networks absolutely can add major latency, have you never had a slow Zoom call? It's because of congestion building up and radio interference, not Zoom's software. That's what leads to things like 1,000 ms latency, which makes back and forth conversation very difficult. Moderate-to-major perceptible latency issues in conversation are always because of the network.
And yes some products do time stretching but that's also what people often call glitches because it's very weird.