I too am an engineer, and unlike yourself, have spent my life dedicated to shooting, hunting, and competing with centerfire rifles... Not everything is about the numbers.

There indeed is such a thing as "inherently accurate". The .270win vs. the .308 win may not be a good example since there are a LOT of reasons why the .308 is considered to be more accurate than the .270, but indeed, there is such an animal as "inherent accuracy". (Military snipers might be required by NATO to use the 7.62x51mm, but benchrest shooters aren't, and there's a reason you see a LOT more .308's than .270's-come shoot sometime and find out). Inherent accuracy is an easy way of saying that on average, more of the variables line up with the optimum conditions than not, whether it's a set of conditions around the bullet itself or around the rifles it's most commonly chambered in.

Much of it comes down to answering the question "are the conditions optimized?" MANY variables play into this question. Choosing a specific CARTRIGE might mean any one of 1000 different brands of powder, charge of powder, brand of primer, bullet, case, bullet weight, or bullet design. Then throw in a specific RIFLE, now adding in rate of twist, barrel material, barrel polish, barrel length, forcing cone design, crown design, barrel stiffness/design etc etc. Does your bullet weight, length, material, and design match up with your rifle's twist rate? Does your bullet material provide enough drag down the barrel to match up with your powder's burn rate? Does your barrel length match your powder burn rate? Is your barrel of high quality, minimizing metallurgic dislocations in grain structure, ensuring uniform heat transfer and expansion upon firing?

There are a million different variable combinations to consider, promising countless hours of calculation and evaluation , when it's MUCH easier to take two rifles out to the range with 4 different types of ammo for each and within 100 rounds tell you which is the most accurate combination.

Consider the .223 remington vs the .22-250. Both produce VERY similar numbers as far as projectile velocity and energy, however, most .223's will be produced with a 1 in 8 to 1 in 10" twist, while .22-250's typically lean above 1 in 10" towards 1 in 12" or 1 in 14". Why is that? Without the experience, you may think both rifles are interchangable, then start feeding 55grn ballistic tips to the .22-250 and wonder why your groups suck compared to the same 55gr load from the same brand and model rifle chambered in .223.

Or ask the opinions of your average hunter, which is a more suitable hunting round, the .30-30 win, the 7.62x39mm, or the .243win. The universal answer will be the .243win, while all 3 have similar muzzle energy, and heck 2 of them are even the same caliber. The 7.62x39 is "known to be inaccurate" because it's most widely available in low quality semiautomatic's like the SKS or AK-47 or the Ruger Mini-30 and not commonly used with a scope, while the cartridge itself is capable of extreme accuracy. The .30-30 is most commonly chambered in lever action rifles, which also don't commonly wear a scope, and require round nosed bullets, providing poor ballistic coefficients. Why is the .243 assumed to be more accurate then? Because it is commonly found chambered in modern bolt action rifles sporting a telescopic sight and firing modern spire pointed bullets... Combinations that make the AVERAGE .243 rifle found on the market much more accurate than the AVERAGE .30-30 or 7.62x39mm rifle.

At the end of the day, I can assign numbers to almost ANY aspect of a rifle's accuracy, and I can build a comparison to help me pick out THE PERFECT RIFLE FOR ME, however, in my experience, there is a LOT more value in taking 100yrs worth of empirical observation to heart as a starting point.

You can't put numbers to EVERY aspect of shooting. There is no "law of big game hunting" that will let you calculate the amount of energy you need to place within a certain distance of a creature's heart to assure a kill. I have killed deer in TX with a .223, deer in KS with a 9x19mm carbine, and deer in colorado with a .375H&H mag. None of those 3 rounds would EVER be recommended for deer, but they all do the job.

At the end of the day, yes, most of the "standard" big game cartridges are no more capable than the other when it comes to practical hunting applications. However, there's more than one way to skin a cat, and for certain cats and certain cat skinners, one technique works better than another. Don't necessarily assume that you can calculate your way into 1000yrd shooting.