Given that a protein needs a very exact number of each amino acid to be synthesized, for essential amino acids like Methionine, I would expect their consumptions to be a bottleneck for muscle building which needs protein. Even if all the other proteins are in good amounts and thus the PDCAAS score is decent, you can drown in a river that’s on average 20cm deep.
I could be misreading but it sounds like you’re misunderstanding how PDCAAS works. If a food contains lots of every other essential amino acid but only (say) 30% of the required amount of methionine, then its PDCAAS will be 30. If the PDCAAS is (say) 90%, that means it contains at least 90% of the requirement for every essential amino acid, not just 90% on average.
I could be misreading but it sounds like you’re misunderstanding how PDCAAS works. If a food contains lots of every other essential amino acid but only (say) 30% of the required amount of methionine, then its PDCAAS will be 30. If the PDCAAS is (say) 90%, that means it contains at least 90% of the requirement for every essential amino acid, not just 90% on average.