Hypothesis: usage of the word "listserv" to mean "mailing list" generically is a shibboleth for non-technical Internet users of a certain age.
LISTSERV was the first mailing list management software, so you'd think that everybody who used the Internet before 1997 or so would call mailing lists "listservs". However, I don't think I've ever heard a programmer use the term "listserv" in the generic sense — at least not since the 90's, when LISTSERV itself was still in widespread use. Even back then, I think programmers and sysadmins mostly restricted its usage to mailing lists managed by LISTSERV specifically (as opposed to majordomo, lyris, mailman, or a plain sendmail alias).
(Speculation as to the reason for this distinction: non-technical users have a greater tendency to conflate general classes of software or protocols with specific instances of them. Example: the belief that a blue "e" is the icon for the Internet.)
Conversely, of course, kids who started using the Internet after web-based social software supplanted email and Usenet obviously don't even know what a "listserv" is. Unless/until they start working with some old fogies who use the term, I suppose.