Broken bones scale, but not in full, drastically backscale (well it depends how bad the break is, a light fracture like Jonathan got from Tarkus and complete shattering of a bone to dust like Dio did to Jonathan early on are obviously two very different things for example).
Take whatever is being scaled to, then give him but a fraction of it.
Kira the same, he doesn't scale to Star Platinum in full, especially not one who was dying but still floored him and the second time was so casual the ****** even did a cool 180, and it crippled him, one punch shattered his fist, as in, literally cracked it apart to the point it was teetering on falling apart.
But, I do think Giorno should be upgraded, worse case scenario he has a street feat, best case scenario he backscales heavily off Green Day.
But I've been looking into that for the upcoming ap and scaling CRT and eh, it's a possibly at best, as in, it's hard to say if Green Day even scales to GE to begin with.
Though it did enough damage to Giorno where I'd wager he backscales to the point he's no longer within 8-C, 9-A maybe, and that's at best.
The damage he took from a few Green Day blows is even being undersold, the old scan isn't accurate, the newest translation says exactly what happened and it ****** him up, the accurate translation says his subclav artery was torn, his lung had a hole in it, his femur was broken along with four ribs and a hand.
For the time being, just slap street on Giorno for the consistent vehicle accidents he's been and walked off without so much as a scratch (one of which completely ****** the vehicle, Ciocolatta dropping a corpse on the moving vehicle from a helicopter which caved the top in) and we'll get into 9-A/8-C durability scaling off Green Day in the upcoming thread, given both GE and Green Day will be tweaked at least a tad then anyway.
If you want to discuss future revisions with me in detail, you're free to add me on Discord of course.