I wonder if this is still true. Whenever I go to hook Win32 API functions, I use an off-the-shelf length disassembler to create a trampoline with the first n bytes of instructions and a jmp back, and then just patch in a jmp to my hook, but if this hot-patch point exists it'd be a lot less painful since you can avoid basically all of that.

Though, I guess even if it was, it'd be silly to rely on it even on x86 only. Maybe it would still make for a nice fast-path? Dunno.