[atlas] tag "system: IPv6 Works"

I just joined the RIPE-Atlas fold with probe #35105 and am still learning the ropes. My public-facing internet servers are all IPv6-only. That means that the only meaningful measurements of my systems come from IPv6 capable probes. I was surprised to see that IPv4-only probes would be scheduled to send IPv6 pings, traceroutes, nslookups etc. Even when I added "system: IPv6 Works" to the include tags and "system: IPv6 Doesn't Work" to the exclude tags I still got some IPv4-only probes assigned. Are those tags for future use and not wired up yet? Are the IPv4-only probes I'm seeing in my test runs there because their status changed recently and previously they were IPv6 capable?  -wolfgang