I think I can provide some insight, but you might already know some or all of this.
In case you did not see it, an upfitter kit has been released for the 2024 HDs that puts the switch bank in the center of the dash under the climate control, above the center console. It does not fit the AT4 and Denali trucks, presumably this applies to AT4X as well. https://404parts.com/products/2024-silverado-sierra-hd-upfitter-auxiliary-switches-package
For the kit you linked to, 404Parts has put all the individual GM part numbers together that usually go into a full kit, minus the replacement trim panel, which isn't available yet. This includes the switch bank, the fuse block, the power cable, and the hardware kit.
They are having you hack into your center console or on the gauge cluster trim panel, (shown above), to locate the switch bank. To make this work you also have to purchase an extension harness as well. I don't know if it would be possible to cut a hole for the switch bank in the AT4,AT4X,Denali knee bolster for a solution similar to the previous years models.
Supposedly there will be a kit out in 2025 that includes a replacement trim panel for the AT4,AT4X, Denali.
GM released a new upfitter integration bulletin for this, 193d, on May 30, 2024. The previous version, 193c, was published on January 31, 2024.