Its not. Prolly akin to late Houtians
Jack's opening move was to drop a meteor to destroy the mountain MC was standing on. That alone puts him probably at MX or PX considering the presumably EX we saw if the MC went through a Devil Outbreak after finding out that AI fridged herself can only what? Throw lightning bolts?
During the fight they punched each other through the mountain and into lava, and somewhere around all of that they created a two mile wide crater from that mountain.
At the climax of the fight, before the Transformation, Jack transformed a volcano to use as a cannon installation against the MC. The MC response range from copying Leona's move which is expanding millions of Blade aura to create a defensive dome, or creating a defensive array that burns everything around it and then holds Jack in place on the sky and reverse gravity so that all that 'cannon balls' hit him instead, or literally deflect, and this is explicitly stated in the text, hundreds of cannon balls every
tenth of a second by swinging your weapon.
Not even the two PH we know, Long Chen (who is stated to be at the midst of ascending into an EX since he now had an aura and was just bottlenecked because he was in a Danger Zone) and Liu Yutai (the Bloodhunter) shows feat anywhere
near this.
This is without even taking into account when they both actually transformed. Him punching the
air was enough turn the mountainside beneath the MC and everything in sight into gravel. And you catching that strike in the Midorikatai route was enough to shake the island you were on. You then proceed to exchange that same punch at hundreds of blows per second.
That should be, at the very least, PX level of fighting. Destroying mountains are usually above the capability of cultivator in the Golden Core Formation stage, of which Shangtians are an inferior version of.