I’m asking because the reasons seem dumb to me, which is why I’m asking people smarter than I am about low-level memory management if they’re legitimate.

The article doesnt say anything about the JVM accessing other processes memory though.

JIT compilation can happen at any time. The runtime wants to create a native version of a previously interpreted snippet of code when it is called frequently enough to warrant this.

The article also describes W^X functionality, which means a region of memory is either executable (x)or writable. On macOS 14.4 violating this either-or condition results in a signal that can not be handled by the process.