OK, so your advice only really applies to top 30 programs then, and there's around 150 last time I checked. Last time I checked, only 30% of students going into IM ended up at a true academic program in any case. So again, this advice will only apply to a minority of students at a minority of programs.
Also, last time I checked, only about a 3rd of IM grads went on to subspecialize. The rest end up as general internists, either inpt or outpt. Again, this means that subspecialization is a concern that affects a minority, not taking into account that there is a greater number that enter IM with plans to subspecialize. The reality is that many won't.
The obsession with subspecialization begins and ends with those who subspecialize, in my experience.
Also, keep in mind, that even at top programs, a lot of the people interviewing you will be general internists. Try not to offend them with an elitist attitude regarding subspecialization.
What probably makes the biggest difference has to do with how academically active residents will be. It's true that those aiming for a subspecialty do more research and such. Between that and having an impressive fellowship match list, is where I think programs care about whether or not you subspecialize. At least that's what I was told being someone who was outspoken about not subspecializing.