What would it be then, for rules to lack verisimilitude? Contain contradictions? Say in one place that magic armor is half the weight of normal armor and in another that it is virtually weightless? Contain multiple discrete subsystems? Like overbearing and pummeling and turning undead all use different mechanics?
The rules are purely abstract, quasi-mathematical constructs. Verisimilitude doesn't mean anything in the context of rules
qua rules.
Questions of verisimilitude arise when you look at the interface between the rules and the imaginary world of the game. Wizards refers to that interface, rather dismissively, as "fluff," and clearly regards it as a matter of secondary importance. But it goes straight to the heart of what we find believable, what doesn't stand up to scrutiny but can be glossed over in play, and what yanks us right out of the imagined reality.
To a great extent, the interface between rules and game world consists of
names. You can put in all the "fluff text" you like, but names trump fluff text every time. Look at how much trouble people have with the idea that you get all your hit points back after a night's rest. Why is that? It's because of the name. "Hit points" suggests "that which you lose when somebody hits you," in other words, physical health. And this is supported by the other names surrounding it: "attack," "hit," "miss," "damage," "healing surge," et cetera.
This issue is by no means confined to 4E, by the way. Every single edition of D&D has gone on at some length about how hit points are this, that, and the other thing, blah, blah, blah. But as long as they're called "hit points," people are going to think of them as physical health and be bothered when the mechanic doesn't behave the way they think it should.