I found out that sly 1 actually has a button cheat code for ressetting the level you're currently in. I tried and yes, you can actually skip boss level cutscenes with it. It might also be faster than loading on some levels to skip the cutscene. It's done by pressing down L2 R2 X down L2 R2 X left O left

Yeah, but its not allowed under current rules, we don't allow leftover dev codes being used in any current Sly 1 categories

We've known about this "newly-" discovered Reload Code for quite a while now, and like Sly 2, it's disallowed until there's demand for Any% w/ Cheats (which is most likely never gonna happen, especially with only one dev code).