A fairly cursory search only turns up a few argumentative message board discussions and some pretty good Howling Tower posts (such as where Steve Winter graphs the discrepancies but backs off the conclusion that the DMG chart is incorrect. This may be widely known and only new to me, but I haven’t found anything definitive or official on it. Based on my number crunching, it looks like the DMG’s central monster creation chart, “Monster Statistics by Challenge Rating”, isn’t in line with the Monster Manual, and if you try to follow it you will get monsters that don’t look much like Monster Manual monsters.
While messing around with monster creation, I started comparing 5e Monster Manual creatures with the 5e guidelines for creating monsters (DMG page 274).