Haven't used trial for quite some time but if I remeber correctly, the trial version had all the features of a single-instance splunk server (so no clustering, separate search heads and so on) just time-limited. Unless something changed lately.
Are you sure your trial period hadn't ended and the server didn't revert to the free version?
"The Enterprise Trial license gives access to all Splunk Enterprise features."
Won't argue here. It's just that the licensing website says that trial is meant for single instance installation. Maybe those features are included but not meant to be used (after all it's just to try the software out, not make a fully blown multi-tiered installations).