Have you imported vAPI metamodel from your vCenter server?
vRO vAPI plug-in comes with only a handful of scripting objects (like VAPIEndpoint); all others are generated dynamically when import a vAPI metamodel from a given vAPI endpoint (eg. vAPI endpoint in the vCenter server).
If you have imported vAPI metamodel and defined one or more vAPI endpoints, but still do not see other vAPI scripting objects in the API explorer, then othe thing to try is to stop and start again vRO UI client. There was such issue with the older builds of vAPI plug-in which was fixed at some point.
As for your other question, could you provide more details on what you mean by 'built directly into orchestrator without needing VAPI'? The current tagging functionality in vCenter is exposed through vAPI, so even if vRO provides some other way to consume these API in scripting (without using vAPI plug-in), at the end it will still call vCenter vAPI endpoint to perform the tagging operations. Of course, these APIs can be designed in a way to 'hide' the actual usage of vAPI, but having such tighter integration has its own drawbacks, and at the moment I'm not aware of any plans to go in this direction.