Bruh... So, I Googled the part number on that alternator (13539726). All the hits, mostly for GM OE replacement part suppliers, show that it's a 170A. It appears to be a direct replacement, as you said. But, it's only 25A more than my stock 145A unit. The sellers on eBay are listing it as a 220A alternator. There's another 170A one, #13534128, that's also being listed as a 220A alternator.
I started digging after comparing the one I have (13539728) with my stock one. First off, it appears that the '9728 is for a truck with the 2.7L turbo 4-cylinder as well as the '20-'21 Cadillac CT4 and CT5 with the 2.0L. This explains the vastly different mounting setup. O'Reilly Auto Parts's website was the only place I found where its output was specified, and it was 220A. I looked up pics of a 2019-2021 6.2 and all showed the alternator mounting setup we have on our trucks. It's just on the RH side of the engine. The ad for the alt I have showed a wrecked Silverado. After running the VIN, that truck had the 2.7L. After more digging, it looks like there's a 13534128 that looks to have the mounting style we have and the GM parts sites list it as a 220A alternator for a '19-'22 truck. I'm gonna research some more on this.
I'm gonna try to return this one on the count of the pulley wobbling, apparently from taking a hit in shipping. Also, in the description, it says "This Part Will Fit These Makes And Models With These Options" and it lists the Sierra 1500 with the KW5 option, ID 13534128. Since this is NOT the 13534128, maybe I can have them swap it for one (and package it better!) if they don't wanna take this one back and refund me.