Great question, and it's really a simple language issue.
"Fully Linux-based solution" means no second, networked, Windows system is required to get sampling data from your Linux applications. (This was the case in previous VTune versions 6.0 and 6.1, as well as with the current VTune 7.0.) It was not intended to mean "As fully functional as the Windows VTune product."
That said, we do indeed have a callgraph viewer plug in, which requires X to function. That software is in extremely limited pilot just now, but will be expanding to include more users/testers over the next few weeks.
If you're interested in kicking the tires on the code, ribeye, let me know here, and I'll see to it that you get it.
The availability of the callgraph viewer plugin software is via means of the pilot test program which is now in extremely limited release, until the end of May.
At about that time, the callgraph viewer plugin pilot test program will start it's second phase, which means it will be made available for a wider audience, and instructions on how to download, register, and use the software will be posted here.
For now, the availability is highly restricted, but interested parties can surely post here and request it, up until Phase 2 starts at the end of May.