What percentage is "sometimes". For example, maybe it is only where two callers are behind the same NAT or some other situation that could be rare relative to the majority of calls.
In any event, it sounds like TURN is not used unless it is needed. The same idea could apply with server forwarding, where forwarding is only used if it is needed. For a small group call, forwarding might not be necessary and full mesh might suffice.
As one user, I would be interested in a full mesh option alongside a server forwarding option.
There is P2P software for small groups I have always used that has a traffic forwarding (relaying) option after the peers are connected, but the default is direct connection, with no need for a relay. The forwarding option is useful for situations where it is needed, but it is not the default. Personally, I have never had to use it.