That really is the heart of the issue...there are no "in-spec" 1911s
There have been a lot of interpretations over the years and a lot of changes to ease manufacture. I think it would be hard to find a 1911A1 that is true to the one introduced 100 years ago.
That is why different magazines will run better in some guns than others
While tolerances may have tightened, I think they have less to do with reliability than say, feed ramp angle, barrel setback (or whatever you call the gap from the end of the breech end of the barrel and the frame feed ramp) and various other specifications.
I have a Kimber (started life as a .45, is now .40 S&W), Springfield Armory (9mm), and Les Baer (.45ACP), all function as close to 100% as possible. When they choke, it's cause they're super dirty, or have ammo issues (my fault, not the gun's). Or something broke (it happens, you shoot enough, you're going to break something in your gun).
I think probably almost all manufacturers (or at least the major ones) produce the majority of their guns to spec (nobody's perfect, anytime you're building something, stuff can happen). There's going to be manufacturing discrepancies based on tool wear and other factors but for the most part guns made today, including those from bargain companies are built to a very high standard. We live in a good time to be gun nuts.
Most times I've seen feeding or extracting issues with these guns (1911 type), it's extractor related. Amazing how much trouble a single little part can cause. Once in a while the magazine is hitting the ejector when inserted. Both of these issues are easy to fix.
Other times it's springs (9mm 1911 with a 14lb or 15lb recoil spring will have week ejection, install a 9 or 10lb spring and it runs like a top). Again easy to fix.
Combine these issues and it may seem like your gun is a super lemon that won't ever run. 9 times out of 10 it can be made to run well with a little attention. You just gotta know what to pay attention to or know someone who knows what to pay attention to.
Seeing people sending their guns back for warranty service for extractor or spring issues is a pet peeve of mine. If there's something actually wrong, send it back. Sending them back for warranty service due to springs or extractor issues or anything else that can be easily addressed by an owner only increases operating costs for the manufacturer and when that happens, they raise prices. Yes it should work from the factory, but seriously, you don't send your car back to Ford cause the tires need air do you?