Well, if Phantasm is possible, then I'm certain Extra is as well.
Phantasm is about same difficulty, to be honest. Most of it is about the same, extra has four cards which are harder to no-vert (Oni & Oni, Wizard Fox Thoughts, 12 General Gods, and Unillateral Contact), Phantasm gets Danmaku Bounded Field and bomb-immune midboss to make up for it (along with Mesh of Light and Darkness which
can force you to bomb more than expected on rare occasions), all in all it's very very reasonable. I got to the last couple of seconds of Border of Humans and Youkai twice before deciding to give Extra a few tries despite Wizard Fox Thoughts being complete random pain, and both of these Phantasm runs had deaths with full bombs, total failures vs. Ran's second card, inexcusable mistakes vs. Spiriting Away, etc.
edit: long story short: GIL's no-vert Phantasm run would be his most overrated achievement if not for the Border of Life and Death timeout which is just ridiculous. But Phantasm no-vert itself is probably easier than UFO hard.