The test writes 500 packets per family and asserted exact-count
delivery within a 5s window, even though its own comment says "Some
packet loss is acceptable for UDP". On FreeBSD/QEMU runners the writer
loops cannot always finish all 500 before the 5s deadline closes the
readers (we have seen 411/500 in CI).
The real assertion of this test is the routing check — IPv4 peer only
gets v4- packets, IPv6 peer only gets v6- packets — which remains
strict. Replace the exact-count assertions with a >=80% delivery
threshold so runner speed variance no longer causes false failures.
