In some ways yes, but it is only applied to functions where they call no other functions and thus "nobody" will ever know they never moved the stack pointer any

In some ways yes, but it is only applied to functions where they call no other functions and thus "nobody" will ever know they never moved the stack pointer anyway. In those situations moving the stack pointer is just pointless extra work because it is a value that will never be used and then just restored to its original value. I say "nobody" because in particular signal handlers (Which are basically just userland interrupts) can interrupt any part of userland code. However since they are generated entirely by the kernel it is easy enough for the kernel to obey the redzone and place the signal handler 128 bytes above the stack pointer, so in practice this isn't that big of a deal.