You are right. This is missing both in the documentation and cli output.
I expanded my test a bit and it's version 5 it's sending:
[root@space-XXXX ~]# tcpdump -vvvvvni eth0 port 6343
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
20:48:25.390592 IP (tos 0x0, ttl 255, id 288, offset 0, flags [none], proto UDP (17), length 272)
X.X.1.5.50035 > X.X.1.110.sflow: [udp sum ok] sFlowv5, IPv4 agent X.X.1.5, agent-id 16, seqnum 288, uptime 1213994542, samples 1, length 244
flow sample (1), length 208,
20:48:32.104573 IP (tos 0x0, ttl 255, id 289, offset 0, flags [none], proto UDP (17), length 296)
X.X.1.5.50035 > X.X.1.110.sflow: [udp sum ok] sFlowv5, IPv4 agent X.X.1.5, agent-id 16, seqnum 289, uptime 1214001257, samples 1, length 268
counter sample (2), length 232,I will push information back that documentation and feature explorer should be updated to reflect this.... but no promises about it being fixed.