You don't. That would require some fundamental changes to the way PS loads and works. not sure what you are getting at, though. It's pretty much like any desktop app behaves. Most of them just don't take as long as PS.
Sorry, based on my experience with coding, I am near certain that there is no programatic reason why Photoshop, or any software, absolutely has to force focus while loading in order to function.
Just as a test, I opened Clip Studio, LibreOffice, Firefox, and a few other programs, and with all of them I can switch away to other programs while they load. If Photoshop is doing something that necessitates focus in order to function after loading, it is doing something exotic and I would be interested to know exactly what that is.
The only part of your claim that I agree with is that everything else I tested load so much faster than Photoshop that I had to move quickly in order to test them.