Well, I think that observation was slightly tongue-in-cheek, based solely on the 2018 thing. But he also goes on to say that GMs (or at least, the front office) have such a larger role when it comes to in-game decisions these days that they are less likely to be fired for that. And also that tanking teams generally stay the course.
It has certainly worked a few times, just no way to actually say that was the thing that made the difference. For all we know Pat Corrales might have gotten the same result in '83. Though this team does feel a lot like that one! (Not ancient, but veteran, and semi-successful - at least last season - but still feels stale.)
In any case, if Joe isn't managing for his job this month he's definitely managing for it next year. I'm not sure he'd be that great a candidate for other jobs either, once you eliminate the tanking teams and the lower-paying teams (which also overlap of course). Unless the Marlins want him back. Doubt David Ross is going anywhere any time soon.
I think when the change does come it will have Fuld's fingerprints all over it. (It could also actually be Fuld but why would he want to do that really.)