Thanks for the info. I'm not particularly familiar with common JIT applications, but I suspect that this use-case is actually more niche than may think.
The problem is that the example presented requires a memory page with write + execute permissions (at the same time). I suspect many JITs don't do this for security reasons (and to deal with OSes which don't allow it), as it may make it easier for an attacker to gain arbitrary code execution.
It's likely that many JITs toggle between write and execute permissions, rather than have both enabled at the same time. Whilst this reduces attack surface, changing permissions on allocated memory requires syscalls, which are quite expensive in terms of performance.
The scenario presented in the article avoids the impact of syscalls, to maximize performance, leaving only the impact caused by the processor itself. If a JIT isn't overly concerned with this type of security, using write+execute memory could be a way to avoid syscall overhead. On the other hand, if a JIT does toggle permissions, the syscall overhead is likely much more significant than overheads caused by the processor (although the techniques shown might still help depending on how the JIT engine works).