It sounds like CR is being used as "you must be this tall to ride this ride" sign, which I can see some merit to.
There are definitely times it'd be handy to have a note like "Hey, don't use this monster until your party has access to
cure blindness or
lesser restoration or
stone to flesh." Similarly for monsters back in the day that were invulnerable to non-magical weapons.
That said, if flat math works the way it's advertised, we don't really need it for normal monsters. In 4e or Pathfinder, hitting a monster a few levels above you can be difficult. But, if the math was actually flat, 1,000 XP of monster should be 1,000 XP of monster regardless.
Even with things leaning away from flat match, as they were in the last packet... I'd still rather have specific notes on certain monsters (an asterisk on the XP value, if you will), than a CR value on every monster that means something different each time.
It'll probably be harmless enough in practice, though. As long as the XP values are good, the CR they're describing will come out in the wash.
I very much like how, at about 41:20, the level of complexity for the base D&D5e game is described as (paraphrased): "Rules cyclopedia with the d20 mechanic and slightly more complex monsters added on. A little bit more because classes have skills now and a few more class features." For me, that's not bad. Not bad at all. That might actually hit my gaming sweet spot.
Yeah, that actually sounds pretty good. We'll see if they can hit that
Cheers!
Kinak