Must chicken feed strictly follow the protein-to-energy ratio and lysine-to-energy ratio?

Back when I was in school, the teacher emphasized that livestock and poultry eat to meet their energy needs, and when formulating feed you must design the formula according to the recommended protein-to-energy ratio and amino acid-to-energy ratio; in actual production I have found that many people do not do it this way, and their protein-to-energy ratio and amino acid-to-energy ratio differ quite a bit from the standard. For example, for fast-growing yellow broilers at the grower stage, some achieve a protein-to-energy ratio of 63g/Kcal, while others achieve 60g/Kcal; how can there be such a big difference, and does it affect production?
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Formulas must be adapted to local conditions.
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Not necessarily, it varies greatly!
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Look at the amino acid balance.
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Right, you have to adapt to local conditions according to market needs.
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The protein-to-energy ratio is very important in chicken feed, because energy generally determines the chicken's feed intake.
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Is the protein-to-energy ratio positively or negatively correlated with the chicken's growth and weight gain?
If the protein-to-energy ratio is a bit lower, does the chicken get a bit fatter (that is, with slightly higher energy and slightly lower protein, will the chicken be a bit fatter?)
There is no way to do a feeding comparison trial, so I ask experienced people for guidance!