I only looked at the first and last link so far, neither supports your claim.
The first one essentially says that some subgroup of older people have lower nutrient intake in general, and that it includes lower protein intake. After a quick glance, it does say "below recommendation" but does not offer evidence of degraded health. In other words, it could also be that the recommendation is not fit for older people. The same article also says that overall, older people have "better" nutrient intake. By the way, nutrition recommendations vary vastly from one country to another, including across developed countries.
The last article says that increased protein intake made no difference in the experiment, which directly contradicts your claim.
This does not motivate me to check the other links, or to believe your claim.