The upshot is that the studies saying your body can only use 45g of protein per meal for muscle synthesis are mostly based on fast-acting whey protein shakes. Stretching out the duration of protein metabolism (by switching protein sources and/or combining it with other foods in a gradually-digested meal) can mitigate the problem quite a bit.
As a counterpoint, take a look at this article: https://peterattiamd.com/protein-anabolic-responses/
The upshot is that the studies saying your body can only use 45g of protein per meal for muscle synthesis are mostly based on fast-acting whey protein shakes. Stretching out the duration of protein metabolism (by switching protein sources and/or combining it with other foods in a gradually-digested meal) can mitigate the problem quite a bit.