I consulted "The Chart" along with many other resources before deciding on purchasing my M&P15. It is just one of many helpful resources available when you are gathering facts pre-purchase.
I knew what features I was looking for and how much I wanted to spend and it helped me save time and effort and money finding which M4 met my needs.
Many of the parts on the chart will have nothing to do with how accurately it will shoot(how many benchrest shooters use chrome-lined barrels?
) or even possibly how reliable it will be.
But as far as reliability is concerned, if it has all the internals listed that have been 100% proofed and inspected, I think the chances of getting a lemon will be greatly reduced.
And all this "upper tier/lower tier" stuff is a bit misleading. The Bravo Company is one of the lower priced offerings and has all of the mil-spec components if not more than the highest priced choices. "Upper tier" doesn't have to mean higher priced.
Recently ran my Smith at a carbine competition and took 2nd place overall at 96% of the high score competing against many compensated race guns. Ran 450rds in a couple hours with no maintanence and no malfunctions whatsoever. It didn't have all the "chart goodies", just the ones I was looking for. I'm happy with my choice.
So as long as your choice of AR's meets your goals and expectations who cares what rollmark it has or whatever the "place" it has on the chart. If it doesn't, maybe a slight parts upgrade is all that is needed to make it 100%.
There is nothing wrong with "The Chart", just with people who think it is the only resource out there.