It's been my experience that exceedingly few pathologists, and thus exceedingly few institutions, have exclusive subspecialty sign-out at all times. Many of the big names in a given organ system still, at least occasionally, do some general sign-out. It's also been my experience that most employers (academic and private, as well as community) want someone who can reliably and confidently sign out more than 1 organ system, if only for coverage purposes. With the exception of megalabs with multiple subspecialty goons and oceans of cases, exclusive subspecialty signout just doesn't make good sense, and working like that for an extended period could make one less employable in any other setting.
It's also been my experience that even in mid-sized private and academic groups which have 1 or 2 heme, neuro, peds, GI, breast, etc., pathologists that at least at times those cases are not seen by said subspecialty trained pathologists -- it's still a matter of who's available, who's on vacation, and the confidence level of whoever's handling cases. These labs still market themselves as having subspecialists..which they do, and difficult cases would still go to them..but it's not automatically exclusive.
So while I agree that most people (clinicians & patients) would prefer their cases be seen by a pathologist with subspecialty experience/training in their particular organ system, as far as I can tell as a global effort it's impractical from a training and job-market perspective. There just aren't enough cases condensed into small enough areas in enough parts of the country/world to justify exclusive subspecialty signout. Maybe when telepathology becomes practical and widespread? And of course, many of the so-called subspecialties don't "technically" even exist as they have no accredited fellowship, though that's not really the point.
Makes me wonder if the same has been said about other specialties' subspecialists -- though for the moment we still have internists and general surgeons, and apparently an adequate market for them.