Averages aren't necessarily much use here, as there are a lot more opportunities for small video calls than for large ones.

If a team of seven has one team meeting and each non-manager has a one-to-one with the manager, the average number of people in a call is ~three. But they're still not going to use a system that can't cope with seven in a call. And they won't have any calls with more than seven participants even if the software can scale to dozens.

(It's also worth noting that Zoom have shown that it's possible to develop "video conferencing" UX than scales to hundreds of participants. I have no idea whether they do this by naively scaling up or by radically changing the way the conference works past a threshold number of participants, but as a participant I don't care)