deep inhale

WINE IS NOT AN EMULATOR

It is a translation layer. All it's doing is intercepting syscalls embedded in the executable process by presenting what looks like an interface for the kernel it is trying to call, but is actually a translation layer to the true host kernel, mapping the Windows syscalls to their near-equivalent for the Linux kernel. This differs from emulation as the calls are being translated at a higher level whereas emulators translate the low level machine code sent to the processor.

So Proton and Wine essentially just pretend to be the core Windows processes and services a Windows environment provides to applications. It's a Windows interface to a Linux kernel on the backend. And virtually every syscall on Linux will always be faster than on Windows/NT. So you get faster syscall responses with a neglible and wholly insubstantial added overhead that I would reckon is hard to quantify because it is in fact so damn small that the only way I can think of to observe it is to attach a debugger, which slows down the application process notably so that human's can peer into the execution stack.

TL;DR: no, Windows applications have theoretically been faster on Linux than they ever were on Windows since Wine's inception.

Others replied about WINE translation layer, but once binary is loaded in memory the kernel juat runs the code it does not care that it is linux or windows code, because to the systembit is chip instructions. It is why LinuxOS was fully able to run DOS way back when

One would think that, but I've seen many claims that it actually runs faster. I wouldn't know personally, I haven't used Windows in 5 years

It's not really emulation. It's running on the same architecture and most of the windows libraries can be used as is with mostly only the win32 library that needs to be wrapped. That already existed for years as wine. It's mostly graphics and peripherals that are broken.

The most important thing proton added to improve gaming was a DirectX translation layer that translates to Vulcan and also loads of fixes and additions to wine.

Not a lot of games run faster but apparently in some situations, the Vulcan precompiled shaders seem to run better than native windows, although that probably means they could make their native version better as well. For older games, the Vulcan translation layer is a lot more efficient and faster than native. Also CPU and IO heavy games might run faster on the Linux kernel.