John Marino is working on versioning libc, and as part of that process, libc is no longer loaded into executable memory.  Here is I think an explanation of lib versioning that may apply, and of course moving things that aren’t supposed to execute, out of executable memory areas, is good for security.  There’s more on that topic, too – W^X may be a similar example.

This is a complicated topic that I’m not part of, so suggest better descriptions in the comments, please.