Though I can not give specific examples in terms of numbers, I have seen indications by folks who know that some things that work in ultra-high precision, BR type rifles can have no discernible effect in "normal" guns.
UncleNick has discussed runout as one such example, IIRC. Small runout makes "big" (percentage big) changes in group size in a rifle that shoots tiny groups but much more severe runout makes no detectable difference in "normal" guns.
In other words, a normal gun might be capable of 2/3s MOA, for example. A BR gun might shoot 1/8 MOA at 100 yards. Getting that 1/8th requires considerable prep, extreme care and expensive dies/equipment. Shooting that same ammo in the "normal" gun gets you... 2/3 MOA. Using collet dies gets you.... 2/3 MOA.
In theory, better. In practice, irrelevant. Not if you're using that BR gun, but a normal gun.
Also, there's the idea of "OK, I cooouuuullllddd get better groups, like 2/5th MOA if I did A, B, C, D, E, F, G.... but I'm only shooting at deer (or even woodchucks) so I can get 2/3 MOA by doing A, B, and C and skipping all the rest. So, why bother, all my targets are MUCH bigger than 2/3 MOA.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.