Axl can only dream of sounding that good. Mrs. Miller would have done a better job.
Axl deserves more credit for learning another bands music so quickly. That’s not easy even for a musician in his twenties. We don’t learn and retain as quickly in later years. I certainly don’t at 50 and I never drank & drugged like Axl.
That said, he doesn’t have the range or precision of the other guy. He’s doing pretty well as a fill-in.
I wonder if Axl was stunt cast for the attention and because they had these dates to which they were already committed. Then they’ll look for someone else for the long-term, like that guy from Krokus. Has anyone heard? I doubt Angus will hang it up and if people are still willing to pay to see him/them, why should he?
Or heck, there’s the off-chance 
Axl will blow it up with GNR and he’ll join AC/DC on a more permanent basis.
I listened to “Back in Black”…not bad, though the lead isn’t as crisp as Angus’, and Caperna has this annoying twang to his voice.
ETA: On the AC/DC vids, what did Axl do to himself (now)?