Michael,
You are correct - OCUM 6.x is currently not supported.
At the time of the Snap Creator 4.1 release OCUM 6.x did not have any exposed APIs that we could use to make calls to OCUM.
(These APIs are now avialable)
As a result the only version of OCUM supported in Snap Creator is the older 5.x version.
I'll send this note onto product management and also send along your suggestion about documenting this.
We just released revised docs yesterday, so it likely wouldn't be until the next doc refresh.
OCUM 6.x was planned for the next major release, but there has been a shift in our roadmap as we work towards our next generation Snap Creator.
As this time I don't think support is planned for Snap Creator 4.x, but I'll bring it up.
Thanks!
John