You (and others) have been told incorrectly:
My source is a nutrition professor who is teaching according to what the American Dietetics Association says. Quite possibly she's/they're wrong though--Who told you (this goes for any of you) that there is a cap on the amount of protein you are able to absorb at once?
Wait.. why are you quoting yourself?
Anyway, I won't even get into who your professor is, their accreditation, how long ago they learned what they're still regurgitating to class after class, etc.
Let's be reasonable, because I'm not looking up any citations:
Milk versus water - they aren't going to affect protein absorption significantly. The post insisting that milk proteins have a low availability can cite that, or we can drop it. Milks don't vary that much, mammal to mammal. How do babies survive without formula?
Your body can effectively handle a reasonable amount of protein; it certainly doesn't top out at 20g. I think the post about 'how much your body can actually use at one time' is one of the most relevant.
Which leads me to explain the snarky intro about your professor. Your logic conveniently drops off right after the point of interest. I don't know if it's your fault or the professor's, but let me clarify. Amino acids are not stored. Amino acids are not excreted, unused. Your body can never 'pull' an amino acid out of storage, even in a catabolic state. Amino acids are utilized to the extent the body deems necessary, based on genetics. The rest is converted into the fundamental currency of metabolic energy: glucose.
Most choose to err on the side of caution, which, in the case of muscle growth, means excess consumption of protein. This can be taxing on your liver but if your lifestyle habits reflect that of someone trying to improve their body, this alone will not debilitate your liver.
The '1g/lb/day'
rule is bullshit, too. There is a lot of misinformation on the internet; don't take my word or anyone else's. Get familiar with textbooks and academic journals. Broscience is the polio of our generation.