I just heard that interview with Robert commenting on the singer. I'm not sure, but it sounds more like a sarcastic dig than real praise. Here, starting at around 2:50, GVF is brought up:
"he's pretty good. There's a job for him somewhere" and then he comments about Zepparella and "what a front man... woman".
This sounds very much in line with typical Plant humor, like "the best percussionist Led Zeppelin has ever had, John Bonham - Moby Dick!" Robert had many similar comments about Zep clones in the 80's. I remember him 'helping' Jason's first band which was a clone band, and there were plenty of playful digs at the 'talent'.
And the music review sites claim Robert is "a fan of Greta Van Fleet"? Is that to just connect to young fans, for all young music fans to feel connected to the past greats?
I'm not knocking GVF, but, uh, give a listen to Zebra, or even the first Bonham album, or any clone band from the 80's. GVF is not a Zep clone, it's a Zebra Clone. It's a xerox of a xerox of a xerox. You still get to enjoy the content, but it's not anything like the original.