No, it isn't quibbling over semantics. Nearly all operating systems have facilities to unmap pages from a process' memory space and give them back to the OS. Not swap them out, not ignore them and let them get compressed, give them back. VMS, Win32, MacOS, OS/3x0 (which is rather older than Unix), AmigaOS, RSTS/E, RSX, RT-11. (I believe TOPS-10 and TOPS-20 did as well, but I'm not positive) Unix was, for quite a while, relatively rare in the multi-user OS realm as a system that wouldn't unmap pages, though the general design of Unix programs minimized the annoyance it caused.

Even still, Most Unix and Unix-like systems have caught up with the '80s and will, in fact, unmap pages, freeing them back to the OS and taking them out of the process' memory space. Perl will give back space to the OS if the OS or C libraries support that and a memory block is unused.

Generally speaking, there's nothing wrong with having a series of discontiguous memory chunks mapped into a process. Happens all the time on many systems, and it works just fine. (Holes in mapped address space actually make a number of things mildly safer, which is also nice)