Hello, thank you everyone for your input. Below is the response from the seller for your knowledge:

"Hello Tegmi1986,

that's correct.

I also did some research and saw the same.
Yesterday I spoke with the German S&W importer - he also only knows about slotted screws, but couldn't check because there is no .460 S&W Magnum in stock.

Of course, I know that "normally" slotted screws are used, but I also know that in strong calibers, screws tend to loosen more frequently.
For me, it was logical >> strong caliber >> screws need to be tightened more often >> S&W thinks ahead and uses Torx for this!

The employee of the German S&W importer asked me to loosen the cylinder crane screw and check if it is, like original S&W, a screw with a spring-loaded front pin.
I did that, and it's exactly the case, so someone didn't just randomly screw in any screws! 100% not!

P.S.: if you google Smith&Wesson, side plate, and Torx, you'll find Torx screws from Club 30 as tuning parts. The customer surely didn't do that, but maybe the dealer where the original owner bought it did.
P.S.: according to the S&W importer, the side plate screws are "standard" (from the S&W L-frame), so they could be replaced at any time.

That's all I can say about it."